SwePub
Sök i SwePub databas

  Utökad sökning

AND är defaultoperator och kan utelämnas

Träfflista för sökning "(AMNE:(ENGINEERING AND TECHNOLOGY Industrial Biotechnology Bioprocess Technology)) "

Sökning: (AMNE:(ENGINEERING AND TECHNOLOGY Industrial Biotechnology Bioprocess Technology))

  • Resultat 1-50 av 785
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Munthe, Christian, 1962 (författare)
  • Precaution and Ethics: Handling risks, uncertainties and knowledge gaps in the regulation of new biotechnologies
  • 2017
  • Bok (övrigt vetenskapligt/konstnärligt)abstract
    • This volume outlines and analyses ethical issues actualized by applying a precautionary approach to the regulation of new biotechnologies. It presents a novel way of categorizing and comparing biotechnologies from a precautionary standpoint. Based on this, it addresses underlying philosophical problems regarding the ethical assessment of decision-making under uncertainty and ignorance, and discusses how risks and possible benefits of such technologies should be balanced from an ethical standpoint. It argues on conceptual and ethical grounds for a technology neutral regulation as well as for a regulation that not only checks new technologies but also requires old, inferior ones to be phased out. It demonstrates how difficult ethical issues regarding the extent and ambition of precautionary policies need to be handled by such a regulation, and presents an overarching framework for doing so.
  •  
2.
  • Mayers, Joshua, 1988, et al. (författare)
  • Integrating Microalgal Production with Industrial Outputs - Reducing Process Inputs and Quantifying the Benefits
  • 2016
  • Ingår i: Industrial Biotechnology. - : Mary Ann Liebert Inc. - 1550-9087 .- 1931-8421. ; 12:4, s. 219-234
  • Tidskriftsartikel (refereegranskat)abstract
    • The cultivation and processing of microalgal biomass is resource- and energy-intensive, negatively affecting the sustainability and profitability of producing bulk commodities, limiting this platform to the manufacture of relatively small quantities of high-value compounds. A biorefinery approach where all fractions of the biomass are valorized might improve the case for producing lower-value products. However, these systems are still likely to operate very close to thresholds of profitability and energy balance, with wide-ranging environmental and societal impacts. It thus remains critically important to reduce the use of costly and impactful inputs and energy-intensive processes involved in these scenarios. Integration with industrial infrastructure can provide a number of residual streams that can be readily used during microalgal cultivation and downstream processing. This review critically considers some of the main inputs required for microalgal biorefineries - such as nutrients, water, carbon dioxide, and heat - and appraises the benefits and possibilities for industrial integration on a more quantitative basis. Recent literature and demonstration studies will also be considered to best illustrate these benefits to both producers and industrial operators. Additionally, this review will highlight some inconsistencies in the data used in assessments of microalgal production scenarios, allowing more accurate evaluation of potential future biorefineries.
  •  
3.
  • Skoog, Emma, 1983, et al. (författare)
  • Biobased adipic acid – The challenge of developing the production host
  • 2018
  • Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 36:8, s. 2248-2263
  • Forskningsöversikt (refereegranskat)abstract
    • Adipic acid is a platform chemical, and is the most important commercial dicarboxylic acid. It has been targeted for biochemical conversion as an alternative to present chemical production routes. From the perspective of bioeconomy, several kinds of raw material are of interest including the sugar platform (derived from starch, cellulose or hemicellulose), the lignin platform (aromatics) and the fatty acid platform (lipid derived). Two main biochemical-based production schemes may be employed: (i) direct fermentation to adipic acid, or (ii) fermentation to muconic or glucaric acid, followed by chemical hydrogenation (indirect fermentation). This review presents a comprehensive description of the metabolic pathways that could be constructed and analyzes their respective theoretical yields and metabolic constraints. The experimental yields and titers obtained so far are low, with the exception of processes based on palm oil and glycerol, which have been reported to yield up to 50 g and 68 g adipic acid/L, respectively. The challenges that remain to be addressed in order to achieve industrially relevant production levels include solving redox constraints, and identifying and/or engineering enzymes for parts of the metabolic pathways that have yet to be metabolically demonstrated. This review provides new insights into ways in which metabolic pathways can be constructed to achieve efficient adipic acid production. The production host provides the chassis to be engineered via an appropriate metabolic pathway, and should also have properties suitable for the industrial production of adipic acid. An acidic process pH is attractive to reduce the cost of downstream processing. The production host should exhibit high tolerance to complex raw material streams and high adipic acid concentrations at acidic pH.
  •  
4.
  • Andersson, Viktor, 1983 (författare)
  • Excess heat utilisation in oil refineries - CCS and algae-based biofuels
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The main objective of this thesis is to investigate two different concepts for CO2 mitigation, from a system perspective, in relation to the oil refining industry: CO2 capture and storage; and algae-based biofuels. For all these processes, process integration with an oil refinery is assumed. The oil refinery sector is a major emitter of CO2 and is responsible for 9% of the industrial emissions of CO2 worldwide. Oil refineries have large amounts of unused excess heat, which can be used to satisfy the heat demands of a CO2 capture plant, a land-based algal cultivation facility, or an algae-based biofuel process. The use of this excess heat significantly reduces the cost for CO2 capture, while an economic evaluation for algae-based biofuels has not been made.Since the amount of heat available from the oil refinery´s processes increase with decreasing temperature in the stripper reboiler, it was investigated how much heat was available at different temperatures. It was also investigated how the decreased temperature would affect the heat demand of CO2 capture processes that use MEA or ammonia as the absorbent. The findings show that it is possible to capture more CO2 using excess heat when the temperature in the stripper reboiler is decreased. For the MEA process, the lower limit of the temperature interval investigated showed the maximum CO2 capture rate, while the ammonia process benefitted from a lower temperature than the standard temperature but showed maximal CO2 capture rate above the lower limit. These results are valid only when using excess heat to satisfy the entire heat demand. At the case study refinery, the available excess heat could satisfy between 28% and 50% of the heat demand of the MEA process when treating the flue gases from all chimneys, depending on the temperature in the stripper reboiler. This utilisation of excess heat represents a way to reduce significantly the costs for CCS in an oil refinery. Land-based cultivation of algae proved to be unsuitable for the utilisation of excess heat. Since the cultivation pond is exposed to wind, rain, and cold, the heat demand fluctuates strongly over the year, making the pond an unstable recipient of the excess heat.Three types of biofuel processes based on microalgae and macroalgae were investigated with respect to integration with the oil refinery. For the algae-based biofuel processes, heat integration and material integration combined to increase the efficiency of the system. When two different build margin technologies (with different CO2 emission factors) are employed for electricity production, macroalgae-based biofuel production appears to be the more robust process from the perspective of CO2 due to the lower electricity demands of the algal cultivation and harvesting phases.
  •  
5.
  • Anasontzis, George E, 1980 (författare)
  • Biomass modifying enzymes: From discovery to application
  • 2012
  • Ingår i: Oral presentation at the Chalmers Life Science AoA conference.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • It has now been realized that the road towards the bio-based economy is a one-way street, leaving gradually the oil-based technology and driving slowly towards a more sustainable society. The current non-biodegradable hydrocarbon fuels and plastics will be replaced by new products which will derive from natural and renewable resources. The synthesis of such biofuels and biochemicals is still challenged by the difficulties to cost efficiently degrade lignocellulosic material to fermentable sugars or to isolate the intact polymers. Biomass degrading and modifying enzymes play an integral role both in the separation of the polymers from the wood network, as well as in their subsequent modification, prior to further product development.Our group interests focus on all levels of applied enzyme research of biomass acting enzymes: Discovery, assay development, production and application. Relevant examples will be provided: What is our strategy for discovering novel microorganisms and enzymes from the tropical forests and grasslands of Vietnam? How do we design novel real-world assays for enzyme activity determination? Which are the bottlenecks in the enzymatic cellulose hydrolysis? How enzymes can be used to produce high added value compounds from biomass?
  •  
6.
  • Ask, Magnus, 1983 (författare)
  • Towards More Robust Saccharomyces cerevisiae Strains for Lignocellulosic Bioethanol Production: Lessons from process concepts and physiological investigations
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Dwindling oil reserves and the negative impacts of fossil fuels on the environment call for more sustainable energy sources. First-generation bioethanol produced from sugar cane and corn has met some of these needs, but it competes with the food supply for raw materials. Lignocellulosic biomass is an abundant non-edible raw material that can be converted to ethanol using the yeast Saccharomyces cerevisiae. However, due to the inherent recalcitrance to degradation of lignocellulosic raw materials, harsh pretreatment methods must be used to liberate fermentable sugars, resulting in the release of compounds such as acetic acid, furan aldehydes and phenolics, that inhibit yeast metabolism. This thesis research aimed to identify bottlenecks in terms of inhibitory compounds related to ethanol production from two lignocellulosic raw materials, Arundo donax and spruce, and furthermore to harness the physiological responses to these inhibitors to engineer more robust yeast strains. A comparative study of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) revealed that acetic acid limits xylose utilization in pretreated Arundo donax, whereas the furan aldehydes furfural and 5-hydroxymethyl-2-furaldehyde (HMF) were hypothesized to be key inhibitors in pretreated spruce. The impacts of furfural and HMF on the redox and energy metabolism of S. cerevisiae were studied in detail in chemostat and batch cultivations. After adding the inhibitors to the feed medium of chemostat cultivations, the intracellular levels of NADH, NADPH, and ATP were found to decrease by 40, 75, and 19%, respectively, suggesting that furan aldehydes drain the cells of reducing power. A strong effect on redox metabolism was also observed after pulsing furfural and HMF in the xylose consumption phase in batch cultures. The drainage of reducing power was also observed in a genome-wide study of transcription that found that genes related to NADPH-requiring processes, such as nitrogen and sulphur assimilation, were significantly induced. The redox metabolism was engineered by overproducing the protective metabolite and antioxidant glutathione. Strains with an increased intracellular level of reduced glutathione were found to sustain ethanol production for longer duration in SSF of pretreated spruce, yielding 70% more ethanol than did the wild type strain.
  •  
7.
  • Ylitervo, Päivi (författare)
  • Concepts for improving ethanol productivity from lignocellulosic materials : encapsulated yeast and membrane bioreactors
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations.
  •  
8.
  • Jansson, Ronnie, et al. (författare)
  • Functionalized silk assembled from a recombinant spider silk fusion protein (Z-4RepCT) produced in the methylotrophic yeast Pichia pastoris
  • 2016
  • Ingår i: Biotechnology Journal. - : Wiley-VCH Verlagsgesellschaft. - 1860-6768 .- 1860-7314. ; 11:5, s. 687-699
  • Tidskriftsartikel (refereegranskat)abstract
    • Functional biological materials are a growing research area with potential applicability in medicine and biotechnology. Using genetic engineering, the possibility to introduce additional functions into spider silk-based materials has been realized. Recently, a recombinant spider silk fusion protein, Z-4RepCT, was produced intracellularly in Escherichia coli and could after purification self-assemble into silk-like fibers with ability to bind antibodies via the IgG-binding Z domain. In this study, the use of the methylotrophic yeast Pichia pastoris for production of Z-4RepCT has been investigated. Temperature, pH and production time were influencing the amount of soluble Z-4RepCT retrieved from the extracellular fraction. Purification of secreted Z-4RepCT resulted in a mixture of full-length and degraded silk proteins that failed to self-assemble into fibers. A position in the C-terminal domain of 4RepCT was identified as being subjected to proteolytic cleavage by proteases in the Pichia culture supernatant. Moreover, the C-terminal domain was subjected to glycosylation during production in P. pastoris. These observed alterations of the CT domain are suggested to contribute to the failure in fiber assembly. As alternative approach, Z-4RepCT retrieved from the intracellular fraction, which was less degraded, was used and shown to retain ability to assemble into silk-like fibers after enzymatic deglycosylation.
  •  
9.
  • Bergman, Alexandra Linda, 1985, et al. (författare)
  • Heterologous phosphoketolase expression redirects flux towards acetate, perturbs sugar phosphate pools and increases respiratory demand in Saccharomyces cerevisiae
  • 2019
  • Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 18:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: Phosphoketolases (Xfpk) are a non-native group of enzymes in yeast, which can be expressed in combination with other metabolic enzymes to positively influence the yield of acetyl-CoA derived products by reducing carbon losses in the form of CO2. In this study, a yeast strain expressing Xfpk from Bifidobacterium breve, which was previously found to have a growth defect and to increase acetate production, was characterized. Results: Xfpk-expression was found to increase respiration and reduce biomass yield during glucose consumption in batch and chemostat cultivations. By cultivating yeast with or without Xfpk in bioreactors at different pHs, we show that certain aspects of the negative growth effects coupled with Xfpk-expression are likely to be explained by proton decoupling. At low pH, this manifests as a reduction in biomass yield and growth rate in the ethanol phase. Secondly, we show that intracellular sugar phosphate pools are significantly altered in the Xfpk-expressing strain. In particular a decrease of the substrates xylulose-5-phosphate and fructose-6-phosphate was detected (26% and 74% of control levels) together with an increase of the products glyceraldehyde-3-phosphate and erythrose-4-phosphate (208% and 542% of control levels), clearly verifying in vivo Xfpk enzymatic activity. Lastly, RNAseq analysis shows that Xfpk expression increases transcription of genes related to the glyoxylate cycle, the TCA cycle and respiration, while expression of genes related to ethanol and acetate formation is reduced. The physiological and transcriptional changes clearly demonstrate that a heterologous phosphoketolase flux in combination with endogenous hydrolysis of acetyl-phosphate to acetate increases the cellular demand for acetate assimilation and respiratory ATP-generation, leading to carbon losses. Conclusion: Our study shows that expression of Xfpk in yeast diverts a relatively small part of its glycolytic flux towards acetate formation, which has a significant impact on intracellular sugar phosphate levels and on cell energetics. The elevated acetate flux increases the ATP-requirement for ion homeostasis and need for respiratory assimilation, which leads to an increased production of CO2. A majority of the negative growth effects coupled to Xfpk expression could likely be counteracted by preventing acetate accumulation via direct channeling of acetyl-phosphate towards acetyl-CoA.
  •  
10.
  • Westman, Johan, 1983, et al. (författare)
  • Current progress in high cell density yeast bioprocesses for bioethanol production
  • 2015
  • Ingår i: Biotechnology journal. - : Wiley. - 1860-6768 .- 1860-7314. ; 10:8, s. 1185-1195
  • Forskningsöversikt (refereegranskat)abstract
    • High capital costs and low reaction rates are major challenges for establishment of fermentation-based production systems in the bioeconomy. Using high cell density cultures is an efficient way to increase the volumetric productivity of fermentation processes, thereby enabling faster and more robust processes and use of smaller reactors. In this review, we summarize recent progress in the application of high cell density yeast bioprocesses for first and second generation bioethanol production. High biomass concentrations obtained by retention of yeast cells in the reactor enables easier cell reuse, simplified product recovery and higher dilution rates in continuous processes. High local cell density cultures, in the form of encapsulated or strongly flocculating yeast, furthermore obtain increased tolerance to convertible fermentation inhibitors and utilize glucose and other sugars simultaneously, thereby overcoming two additional hurdles for second generation bioethanol production. These effects are caused by local concentration gradients due to diffusion limitations and conversion of inhibitors and sugars by the cells, which lead to low local concentrations of inhibitors and glucose. Quorum sensing may also contribute to the increased stress tolerance. Recent developments indicate that high cell density methodology, with emphasis on high local cell density, offers significant advantages for sustainable second generation bioethanol production.
  •  
11.
  • Zambrano, Jesús, et al. (författare)
  • Optimal steady-state design of zone volumes of bioreactors with Monod growth kinetics
  • 2015
  • Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X .- 1873-295X. ; 100, s. 59-66
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper deals with steady-state analysis and design of bioreactors consisting of a number of completely stirred tank reactors (CSTRs) in series. The study is confined to one consumed (substrate) and one consuming constituent (biomass). The specific microbial growth rate is assumed to be described by Monod kinetics. The death of biomass is assumed to be negligible. Two optimal design problems for a large number of CSTRs in series are studied: to minimize the effluent substrate concentration for a given total volume, and to minimize the total volume for a given effluent substrate concentration. As an appealing alternative to solve these problems numerically, it is proposed to consider the asymptotic case where the number of CSTRs tends to infinity. This is shown to correspond to one CSTR in series with a plug flow reactor (PFR). A CSTR with a sufficient large volume is needed to avoid wash-out of the biomass. The main result is that both design problems for the CSTR + PFR configuration have the same solution with respect to the optimal volume of the CSTR, which is given as an explicit function of the incoming substrate concentration, the volumetric flow rate and the coefficients of the Monod growth rate function. Numerical results indicate that the plug flow approach may be used as a feasible design procedure even for a reasonably low number of CSTRs in series.
  •  
12.
  • Franzén, Carl Johan, 1966, et al. (författare)
  • Multifeed simultaneous saccharification and fermentation enables high gravity submerged fermentation of lignocellulose.
  • 2015
  • Ingår i: Recent Advances in Fermentation Technology (RAFT 11), Clearwater Beach, Florida, USA, November 8-11, 2015. Oral presentation..
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Today, second generation bioethanol production is becoming established in production plants across the world. In addition to its intrinsic value, the process can be viewed as a model process for biotechnological conversion of recalcitrant lignocellulosic raw materials to a range of chemicals and other products. So called High Gravity operation, i.e. fermentation at high solids loadings, represents continued development of the process towards higher product concentrations and productivities, and improved energy and water economy. We have employed a systematic, model-driven approach to the design of feeding schemes of solid substrate, active yeast adapted to the actual substrate, and enzymes to fed-batch simultaneous saccharification and co-fermentation (Multifeed SSCF) of steam-pretreated lignocellulosic materials in stirred tank reactors. With this approach, mixing problems were avoided even at water insoluble solids contents of 22%, leading to ethanol concentrations of 56 g/L within 72 hours of SSCF on wheat straw. Similar fermentation performance was verified in 10 m3 demonstration scale using wheat straw, and in lab scale on birch and spruce, using several yeast strains. The yeast was propagated in the liquid fraction obtained by press filtration of the pretreated slurry. Yet, even with such preadaptation and repeated addition of fresh cells, the viability in the SSCF dropped due to interactions between lignocellulose-derived inhibitors, the produced ethanol and the temperature. Decreasing the temperature from 35 to 30°C when the ethanol concentration reached 40-50 g/L resulted in rapid initial hydrolysis, maintained fermentation capacity, lower residual glucose and xylose and ethanol concentrations above 60 g/L.
  •  
13.
  • Nickel, David, 1990, et al. (författare)
  • Uncertainty analysis as a tool to consistently evaluate lignocellulosic bioethanol processes at different system scales
  • 2018
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Lignocellulosic processes are highly prone to batch-to batch variability, e.g. of raw materials and enzyme activities. This variability can be propagated throughout system scales during process development and optimization, influencing the outputs of bioreaction models, techno-economic analyses and life cycle assessments. As these outputs are the main decision variables for designing and developing lignocellulose-based processes, tools are required to evaluate the influences of process variation at different system scales. Uncertainty analysis quantifies the effects of model input variations on model outputs. It is an effective tool to consistently propagate process variation throughout scales and analyse its influence on model outputs. As an example, we use a model describing multi-feed simultaneous saccharification and co-fermentation (SSCF) of wheat straw. During the process enzymes hydrolyse the lignocellulosic material to release glucose which can be converted by microorganisms into ethanol. To investigate the impact of batch-to-batch variability in enzyme cocktails, we collected literature data on the enzymatic activity of Cellic CTec2. Retrieved data were propagated in models at bioreactor, techno-economic analysis and life cycle assessment scale. We show how uncertainty analysis can be used to guide process development by comparing different modes of operation. The method can identify economically feasible process ranges with low environmental impact while increasing the robustness of bioprocesses with high variation in raw material inputs. Furthermore, uncertainty analysis could help to identify relevant parameters to choose as response variables in experimental designs.
  •  
14.
  • Wang, Ruifei, 1985, et al. (författare)
  • Model-based optimization and scale-up of multi-feed simultaneous saccharification and co-fermentation of steam pre-treated lignocellulose enables high gravity ethanol production.
  • 2016
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 9:1, s. 88-
  • Tidskriftsartikel (refereegranskat)abstract
    • High content of water-insoluble solids (WIS) is required for simultaneous saccharification and co-fermentation (SSCF) operations to reach the high ethanol concentrations that meet the techno-economic requirements of industrial-scale production. The fundamental challenges of such processes are related to the high viscosity and inhibitor contents of the medium. Poor mass transfer and inhibition of the yeast lead to decreased ethanol yield, titre and productivity. In the present work, high-solid SSCF of pre-treated wheat straw was carried out by multi-feed SSCF which is a fed-batch process with additions of substrate, enzymes and cells, integrated with yeast propagation and adaptation on the pre-treatment liquor. The combined feeding strategies were systematically compared and optimized using experiments and simulations.
  •  
15.
  • Ylitervo, Päivi, et al. (författare)
  • Continuous Ethanol Production with a Membrane Bioreactor at High Acetic Acid Concentrations
  • 2014
  • Ingår i: Membranes. - : MDPI. - 2077-0375. ; 4:3, s. 372-387
  • Tidskriftsartikel (refereegranskat)abstract
    • The release of inhibitory concentrations of acetic acid from lignocellulosic raw materials during hydrolysis is one of the main concerns for 2nd generation ethanol production. The undissociated form of acetic acid can enter the cell by diffusion through the plasma membrane and trigger several toxic effects, such as uncoupling and lowered intracellular pH. The effect of acetic acid on the ethanol production was investigated in continuous cultivations by adding medium containing 2.5 to 20.0 g•L−1 acetic acid at pH 5.0, at a dilution rate of 0.5 h−1. The cultivations were performed at both high (~25 g•L−1) and very high (100–200 g•L−1) yeast concentration by retaining the yeast cells inside the reactor by a cross-flow membrane in a membrane bioreactor. The yeast was able to steadily produce ethanol from 25 g•L−1 sucrose, at volumetric rates of 5–6 g•L−1•h−1 at acetic acid concentrations up to 15.0 g•L−1. However, the yeast continued to produce ethanol also at a concentration of 20 g•L−1 acetic acid but at a declining rate. The study thereby demonstrates the great potential of the membrane bioreactor for improving the robustness of the ethanol production based on lignocellulosic raw materials.
  •  
16.
  • Nickel, David, 1990, et al. (författare)
  • Multi-scale uncertainty analysis – A tool to systematically consider variability in lignocellulosic bioethanol processes
  • 2018
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Bioethanol production processes from lignocellulosic raw materials are highly prone to batch-to-batch variations. For example, raw material compositions and enzymatic activities required to release fermentable sugars from lignocellulose vary significantly between batches. To develop lignocellulosic biofuel processes and evaluate their performance regarding economics and sustainability consistently, tools are required to cope with this variability.   In this presentation we will propose a multi-scale uncertainty analysis strategy to propagate input variability throughout system scales. In a first step, we use meta-data obtained from literature to define uncertainties in the process inputs. Utilizing these meta-data, uncertainty analysis is performed on a macro-kinetic model by sampling from the defined uncertain input space. The results of this uncertainty analysis are transferred to process simulations to analyze the impact of input uncertainties on the process mass- and energy balances, and on the economics of building this type of bioprocess. The generated data from process simulations (mass flows, energy integration, and economic data) are in the next step extracted and used as input to an environmental impact assessment of the process. This is done whilst keeping the simulation and systems modeling parameters constant, thus the input variability is propagated throughout the different system scales. The data generated in this integrated approach will then be compared with the variations and uncertainties observed with relevance to the estimated parameters in the process simulation and environmental impact assessment. Based on this consistent strategy, we can analyze the impact of input variability from different system perspectives, identify important bottlenecks for development, and suggest robust and sustainable process designs for different conditions and under given uncertainties.   In a case study we demonstrate how integrated kinetic modeling (in Matlab), process simulation (in SuperPro Designer), and environmental impact assessment together with statistical analysis can be used for assessing how variability in enzymatic activities in bioethanol production can be propagated throughout system scales. A macro-kinetic model is used to describe the enzymatic breakdown of lignocellulose-derived polysaccharides into fermentable sugars (saccharification) and the simultaneous fermentation to bioethanol. We discuss the integration of the simulation results of the macro-kinetic model into the flowsheeting software for mass and energy balance generation, and then further on to assess environmental impacts of the process. We will evaluate different process designs regarding their robustness towards input variability. Finally, we also show how propagated uncertainties at different system scales can be integrated to design experiments at laboratory scale so that these focus on the most important parameters for developing robust kinetic models, and include the parameters that are most important for sustainable design of processes and value chains.
  •  
17.
  • Nickel, David, 1990 (författare)
  • Process development for platform chemical production from agricultural and forestry residues
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • As part of a bio-based economy, biorefineries are envisaged to sustainably produce platform chemicals via biochemical conversion of agricultural and forestry residues. However, supply risks, the recalcitrance of lignocellulosic biomass, and inhibitor formation during pre­treatment impair the economic feasibility of such biorefineries. In this thesis, process design and assessment were developed with the aim of addressing these hurdles and improving the cost-effectiveness of lignocellulose-derived platform chemicals. To expand the feedstock base and reduce operational costs, logging residues served as underutilised and inexpensive raw material. The major impediment in converting logging residues was their high recalcitrance and low cellulose content, which resulted in low attainable ethanol titres during simultaneous saccharification and co-fermentation (SSCF). Pretreatment optimisation reduced inhibitor formation and recalcitrance, and led to enzymatic hydrolysis yields at par with those obtained for stem wood, despite the less favourable chemical composition. Upgrading logging residues with carbohydrate-rich oat hulls increased ethanol titres to >50 g/L using batch SSCF at 20% WIS loadings, demonstrating the potential to further decrease downstream processing costs. To alleviate the toxicity of inhibitors generated during pretreatment, preadaptation was applied to Saccharomyces cerevisiae . Exposure to the inhibitors in the pretreated liquid fraction improved ethanol production during subsequent fermentation. Transferring the concept of preadaptation to lactic acid production by Bacillus coagulans cut the process times by half and more than doubled the average specific lactic acid productivity, showcasing how preadaptation could decrease operational costs. To assess the performance and robustness of process designs against process input variations, a multi-scale variability analysis framework was developed. The framework included models for bioprocess, flowsheet, techno-economic, and life cycle assessment. In a case study, multi-feed processes, in which solids and cells are fed to the process using model-based predictions, were more robust against variable cellulolytic activities than batch SSCFs in a wheat straw-based ethanol biorefinery. The developed framework can be used to identify robust biorefinery process designs, which simultaneously meet technological, economic, and environmental goals.
  •  
18.
  • Skvaril, Jan, 1982-, et al. (författare)
  • Applications of near-infrared spectroscopy (NIRS) in biomass energy conversion processes : A review
  • 2017
  • Ingår i: Applied spectroscopy reviews (Softcover ed.). - : Informa UK Limited. - 0570-4928 .- 1520-569X. ; 52:8, s. 675-728
  • Forskningsöversikt (refereegranskat)abstract
    • Biomass used in energy conversion processes is typically characterized by high variability, making its utilization challenging. Therefore, there is a need for a fast and non-destructive method to determine feedstock/product properties and directly monitor process reactors. The near-infrared spectroscopy (NIRS) technique together with advanced data analysis methods offers a possible solution. This review focuses on the introduction of the NIRS method and its recent applications to physical, thermochemical, biochemical and physiochemical biomass conversion processes represented mainly by pelleting, combustion, gasification, pyrolysis, as well as biogas, bioethanol, and biodiesel production. NIRS has been proven to be a reliable and inexpensive method with a great potential for use in process optimization, advanced control, or product quality assurance.
  •  
19.
  • Brechmann, Nils Arnold, et al. (författare)
  • Pilot-scale process for magnetic bead purification of antibodies directly from non-clarified CHO cell culture
  • 2019
  • Ingår i: Biotechnology progress (Print). - : AIChE. - 8756-7938 .- 1520-6033.
  • Tidskriftsartikel (refereegranskat)abstract
    • High capacity magnetic protein A agarose beads, LOABeads PrtA, were used in the developmentof a new process for affinity purification of monoclonal antibodies (mAbs) from non-clarifiedCHO cell broth using a pilot-scale magnetic separator. The LOABeads had a maximum bindingcapacity of 65 mg/mL and an adsorption capacity of 25–42 mg IgG/mL bead in suspension for anIgG concentration of 1 to 8 g/L. Pilot-scale separation was initially tested in a mAb capture stepfrom 26 L clarified harvest. Small-scale experiments showed that similar mAb adsorptions wereobtained in cell broth containing 40 Å~ 106 cells/mL as in clarified supernatant. Two pilot-scalepurification runs were then performed on non-clarified cell broth from fed-batch runs of 16 L,where a rapid mAb adsorption ≥96.6% was observed after 1 h. This process using 1 L of magnetic beads had an overall mAb yield of 86% and 16 times concentration factor. After this single proteinA capture step, the mAb purity was similar to the one obtained by column chromatography, whilethe host cell protein content was very low, <10 ppm. Our results showed that this magnetic beadmAb purification process, using a dedicated pilot-scale separation device, was a highly efficientsingle step, which directly connected the culture to the downstream process without cell clarification.Purification of mAb directly from non-clarified cell broth without cell separation can providesignificant savings in terms of resources, operation time, and equipment, compared to legacy procedure of cell separation followed by column chromatography step.
  •  
20.
  • Martinez Avila, Hector, 1985 (författare)
  • Biofabrication, Biomechanics and Biocompatibility of Nanocellulose-based Scaffolds for Auricular Cartilage Regeneration
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In about 2:10,000 births the external part of the ear, the auricle, is severely malformed or absent. Furthermore, tumors and trauma can cause defects to the auricle. For patients with dysplasia of the auricle, and especially for children, an inconspicuous outer appearance with life-like auricles is important for their psychological and emotional well being as well as their psycho-social development. Auricular reconstruction remains a great challenge due to the complexity of surgical reconstruction using rib cartilage. Despite the advances in stem cell technology and biomaterials, auricular cartilage tissue engineering (TE) is still in an early stage of development due to critical requirements demanding appropriate mechanical properties and shape stability of the tissue-engineered construct. This thesis has focused on developing patient-specific tissue-engineered auricles for one-step surgery using a novel biomaterial, bacterial nanocellulose (BNC), seeded with human nasoseptal chondrocytes (hNC) and bone marrow mononuclear cells (MNC).Biomechanical properties of human auricle cartilage were measured and used as a benchmark for tuning BNC properties. In order to meet the biomechanical requirements, a scaffold with bilayer architecture composed of a dense BNC support layer and a macroporous structure was designed. Firstly, the biocompatibility of the dense BNC layer was investigated, demonstrating a minimal foreign body response according to standards set forth in ISO 10993. Secondly, different methods to create macroporous BNC scaffolds were studied and the redifferentiation capacity of hNCs was evaluated in vitro; revealing that macroporous BNC scaffolds support cell ingrowth, proliferation and neocartilage formation. The bilayer BNC scaffold was biofabricated and tested for endotoxins and cytotoxicity before evaluating in long-term 3D culture, and subsequently in vivo for eight weeks—in an immunocompromised animal model. The results demonstrated that the non-pyrogenic and non- cytotoxic bilayer BNC scaffold offers a good mechanical stability and maintains a structural integrity, while providing a porous 3D environment that is suitable for hNCs and MNCs to produce neocartilage, in vitro and in vivo. Furthermore, patient-specific auricular BNC scaffolds with bilayer architecture were biofabricated and seeded with autologous rabbit auricular chondrocytes (rAC) for implantation in an immunocompetent rabbit model for six weeks. The results demonstrated the shape stability of the rAC-seeded scaffolds and neocartilage depositions in the immunocompetent autologous grafts. 3D bioprinting was also evaluated for biofabrication of patient-specific, chondrocyte-laden auricular constructs using a bioink composed of nanofibrillated cellulose and alginate. Bioprinted auricular constructs showed an excellent shape and size stability after in vitro culture. Moreover, this bioink supports redifferentiation of hNCs while offering excellent printability, making this a promising approach for auricular cartilage TE. Furthermore, the use of bioreactors is essential for the development of tissue-engineered cartilage in vitro. Thus, a compression bioreactor was utilized to apply dynamic mechanical stimulation to cell-seeded constructs as a means to enhance production of extracellular matrix in vitro.In this work, a potential clinical therapy for auricular reconstruction using tissue-engineered auricles is demonstrated; where BNC is proposed as a promising non-degradable biomaterial with good chemical and mechanical stability for auricular cartilage TE. Although the primary focus of this thesis is on auricular reconstruction, the methods developed are also applicable in the regeneration of other cartilage tissues such as those found in the nose, trachea, spine and articular joints.
  •  
21.
  • Rupar, Katarina, et al. (författare)
  • Solid Phase Micro Extraction Fibers, Calibration for Use in Biofilter Applications
  • 2006
  • Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X. ; 31:2, s. 107-112
  • Tidskriftsartikel (refereegranskat)abstract
    • The main purpose of this study is to develop a SPME calibration method suitable for use in evaluation of concentrations of hydrophobic substances in environmental samples. The analyte used in the experiments was alpha-pinene, a hydrophobic organic compound commonly found in wood, and therefore found in wood storage facilities, wood processing industries and wood based biofilters. The SPME fibres were calibrated for different concentrations of alpha-pinene at different temperatures and relative humidities. The method was used to evaluate the removal efficiency of a lab-scale biofilter.
  •  
22.
  • Ferreira, Sofia, et al. (författare)
  • Metabolic engineering strategies for butanol production in Escherichia coli
  • 2020
  • Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; 117:8, s. 2571-2587
  • Forskningsöversikt (refereegranskat)abstract
    • The global market of butanol is increasing due to its growing applications as solvent, flavoring agent, and chemical precursor of several other compounds. Recently, the superior properties of n-butanol as a biofuel over ethanol have stimulated even more interest. (Bio)butanol is natively produced together with ethanol and acetone by Clostridium species through acetone-butanol-ethanol fermentation, at noncompetitive, low titers compared to petrochemical production. Different butanol production pathways have been expressed in Escherichia coli, a more accessible host compared to Clostridium species, to improve butanol titers and rates. The bioproduction of butanol is here reviewed from a historical and theoretical perspective. All tested rational metabolic engineering strategies in E. coli to increase butanol titers are reviewed: manipulation of central carbon metabolism, elimination of competing pathways, cofactor balancing, development of new pathways, expression of homologous enzymes, consumption of different substrates, and molecular biology strategies. The progress in the field of metabolic modeling and pathway generation algorithms and their potential application to butanol production are also summarized here. The main goals are to gather all the strategies, evaluate the respective progress obtained, identify, and exploit the outstanding challenges.
  •  
23.
  • Huang, Mingtao, 1984, et al. (författare)
  • Engineering the protein secretory pathway of Saccharomyces cerevisiae enables improved protein production
  • 2018
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:47, s. E11025-E11032
  • Tidskriftsartikel (refereegranskat)abstract
    • Baker’s yeast Saccharomyces cerevisiae is one of the most important and widely used cell factories for recombinant protein production. Many strategies have been applied to engineer this yeast for improving its protein production capacity, but productivity is still relatively low, and with increasing market demand, it is important to identify new gene targets, especially targets that have synergistic effects with previously identified targets. Despite improved protein production, previous studies rarely focused on processes associated with intracellular protein retention. Here we identified genetic modifications involved in the secretory and trafficking pathways, the histone deacetylase complex, and carbohydrate metabolic processes as targets for improving protein secretion in yeast. Especially modifications on the endosome-to-Golgi trafficking was found to effectively reduce protein retention besides increasing protein secretion. Through combinatorial genetic manipulations of several of the newly identified gene targets, we enhanced the protein production capacity of yeast by more than fivefold, and the best engineered strains could produce 2.5 g/L of a fungal α-amylase with less than 10% of the recombinant protein retained within the cells, using fed-batch cultivation.
  •  
24.
  • Olofsson, Martin, 1975-, et al. (författare)
  • Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata 
  • 2014
  • Ingår i: Marine Drugs. - Basel, Switzerland : MDPI AG. - 1660-3397. ; 12:4, s. 1891-1910
  • Tidskriftsartikel (refereegranskat)abstract
    • Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L−1 day−1) compared to N-sufficiency (0.11 g L−1 day−1). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.
  •  
25.
  • Danielsson, Per-Erik (författare)
  • Implementations of the Convolution Operation
  • 1982
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The first part of this article surveys a large number of implementations of the convolution operation (which is also known as the sum-of-products, the inner product) based on a systematic exploration of index permutations. First we assume a limited amount of parallelism in the form of an adder. Next, multipliers and RAM:s are utilized. The so called distributed arithmetic follows naturally from this approach.The second part brings in the concept of pipelining on the bitlevel to obtain high throughput convolvers adapted for VLSI-design (systolic arrays). The serial/parallel multiplier is analyzed in a way that unravels a vast amount new variations. Even more interesting, all these new variations can be carried over to serial/parallel convolvers. These novel devices can be implemented as linear structures of identical cells where the multipliers are embedded at equidistant intervals.
  •  
26.
  • Measurement, Monitoring, Modelling and Control of Bioprocesses
  • 2013
  • Samlingsverk (redaktörskap) (refereegranskat)abstract
    • Automated Measurement and Monitoring of Bioprocesses: Key Elements of the M3C Strategy, by Bernhard Sonnleitner Automatic Control of Bioprocesses, by Marc Stanke, Bernd Hitzmann An Advanced Monitoring Platform for Rational Design of Recombinant Processes, by G. Striedner, K. Bayer Modelling Approaches for Bio-Manufacturing Operations, by Sunil Chhatre Extreme Scale-Down Approaches for Rapid Chromatography Column Design and Scale-Up During Bioprocess Development, by Sunil Chhatre Applying Mechanistic Models in Bioprocess Development, by Rita Lencastre Fernandes, Vijaya Krishna Bodla, Magnus Carlquist, Anna-Lena Heins, Anna Eliasson Lantz, Gürkan Sin and Krist V. Gernaey Multivariate Data Analysis for Advancing the Interpretation of Bioprocess Measurement and Monitoring Data, by Jarka Glassey Design of Pathway-Level Bioprocess Monitoring and Control Strategies Supported by Metabolic Networks, by Inês A. Isidro, Ana R. Ferreira, João J. Clemente, António E. Cunha, João M. L. Dias, Rui Oliveira Knowledge Management and Process Monitoring of Pharmaceutical Processes in the Quality by Design Paradigm, by Anurag S Rathore, Anshuman Bansal, Jaspinder Hans The Choice of Suitable Online Analytical Techniques and Data Processing for Monitoring of Bioprocesses, by Ian Marison, Siobhán Hennessy, Róisín Foley, Moira Schuler, Senthilkumar Sivaprakasam, Brian Freeland
  •  
27.
  • Schwarz, Hubert, et al. (författare)
  • Integrated continuous biomanufacturing on pilot scale for acid-sensitive monoclonal antibodies
  • 2022
  • Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we demonstrated the first, to our knowledge, integrated continuous bioprocess (ICB) designed for the production of acid-sensitive monoclonal antibodies, prone to aggregate at low pH, on pilot scale. A high cell density perfusion culture, stably maintained at 100 × 106 cells/ml, was integrated with the downstream process, consisting of a capture step with the recently developed Protein A ligand, ZCa; a solvent/detergent-based virus inactivation; and two ion-exchange chromatography steps. The use of a mild pH in the downstream process makes this ICB suitable for the purification of acid-sensitive monoclonal antibodies. Integration and automation of the downstream process were achieved using the Orbit software, and the same equipment and control system were used in initial small-scale trials and the pilot-scale downstream process. High recovery yields of around 90% and a productivity close to 1 g purified antibody/L/day were achieved, with a stable glycosylation pattern and efficient removal of impurities, such as host cell proteins and DNA. Finally, negligible levels of antibody aggregates were detected owing to the mild conditions used throughout the process. The present work paves the way for future industrial-scale integrated continuous biomanufacturing of all types of antibodies, regardless of acid stability.
  •  
28.
  • Zhang, Yiming, 1986, et al. (författare)
  • Engineering yeast mitochondrial metabolism for 3-hydroxypropionate production
  • 2023
  • Ingår i: Biotechnology for Biofuels and Bioproducts. - 2731-3654. ; 16:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: With unique physiochemical environments in subcellular organelles, there has been growing interest in harnessing yeast organelles for bioproduct synthesis. Among these organelles, the yeast mitochondrion has been found to be an attractive compartment for production of terpenoids and branched-chain alcohols, which could be credited to the abundant supply of acetyl-CoA, ATP and cofactors. In this study we explored the mitochondrial potential for production of 3-hydroxypropionate (3-HP) and performed the cofactor engineering and flux control at the acetyl-CoA node to maximize 3-HP synthesis. Results: Metabolic modeling suggested that the mitochondrion serves as a more suitable compartment for 3-HP synthesis via the malonyl-CoA pathway than the cytosol, due to the opportunity to obtain a higher maximum yield and a lower oxygen consumption. With the malonyl-CoA reductase (MCR) targeted into the mitochondria, the 3-HP production increased to 0.27 g/L compared with 0.09 g/L with MCR expressed in the cytosol. With enhanced expression of dissected MCR enzymes, the titer reached to 4.42 g/L, comparable to the highest titer achieved in the cytosol so far. Then, the mitochondrial NADPH supply was optimized by overexpressing POS5 and IDP1, which resulted in an increase in the 3-HP titer to 5.11 g/L. Furthermore, with induced expression of an ACC1 mutant in the mitochondria, the final 3-HP production reached 6.16 g/L in shake flask fermentations. The constructed strain was then evaluated in fed-batch fermentations, and produced 71.09 g/L 3-HP with a productivity of 0.71 g/L/h and a yield on glucose of 0.23 g/g. Conclusions: In this study, the yeast mitochondrion is reported as an attractive compartment for 3-HP production. The final 3-HP titer of 71.09 g/L with a productivity of 0.71 g/L/h was achieved in fed-batch fermentations, representing the highest titer reported for Saccharomyces cerevisiae so far, that demonstrated the potential of recruiting the yeast mitochondria for further development of cell factories.
  •  
29.
  • Trivellin, Cecilia, 1993, et al. (författare)
  • Quantification of Microbial Robustness in Yeast
  • 2022
  • Ingår i: ACS Synthetic Biology. - : American Chemical Society (ACS). - 2161-5063. ; 11:4, s. 1686-1691
  • Tidskriftsartikel (refereegranskat)abstract
    • Stable cell performance in a fluctuating environment is essential for sustainable bioproduction and synthetic cell functionality; however, microbial robustness is rarely quantified. Here, we describe a high-throughput strategy for quantifying robustness of multiple cellular functions and strains in a perturbation space. We evaluated quantification theory on experimental data and concluded that the mean-normalized Fano factor allowed accurate, reliable, and standardized quantification. Our methodology applied to perturbations related to lignocellulosic bioethanol production showed that the industrial bioethanol producing strain Saccharomyces cerevisiae Ethanol Red exhibited both higher and more robust growth rates than the laboratory strain CEN.PK and industrial strain PE-2, while a more robust product yield traded off for lower mean levels. The methodology validated that robustness is function-specific and characterized by positive and negative function-specific trade-offs. Systematic quantification of robustness to end-use perturbations will be important to analyze and construct robust strains with more predictable functions.
  •  
30.
  •  
31.
  • Perruca Foncillas, Raquel (författare)
  • Evaluation of biosensors and flow cytometry as monitoring tools in lignocellulosic bioethanol production
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The significant environmental impact of the current fossil fuel-based industry is a major concern for society. Consequently, various initiatives are being undertaken to establish a more sustainable industrial model. One example is via the transition from conventional fossil fuel refineries to biorefineries, where renewable raw materials are utilised. Amongst these raw materials, the use of lignocellulosic biomass from agricultural residues or wood has been favoured, as it does not compete with food or land resources. In particular, extensive research has been conducted to produce biofuels such as bioethanol from lignocellulosic biomass, referred to as second-generation (2G) bioethanol.In this thesis work, the goal was to develop and apply new tools to address challenges encountered in 2G bioethanol production. Specifically, the work focused on monitoring the impact of inhibitory compounds and mixed sugars on the fermentation performance of the yeast Saccharomyces cerevisiae.Inhibitory compounds are released during the pretreatment of the lignocellulosic biomass, a crucial step necessary to break down its complex structure and to enhance sugar accessibility This thesis work specifically focused on the redox imbalance induced in cells exposed to furaldehydes such as furfural or HMF. To study this effect, a biosensor for redox imbalance, TRX2p-yEGFP, was introduced into the cells and its fluorescence signal was monitored in real-time using flow cytometry. One potential strategy for enhancing the cells' tolerance to these inhibitors is to prepare them by introducing lignocellulosic hydrolysate in the feed during cell propagation. During this pre-exposure phase, a transient induction of the TRX2p-yEGFP biosensor signal for redox imbalance was observed, which gradually diminished. This indicated that, by the time of cell collection, the cells had adapted to the inhibitor concentration within the culture. To examine whether an increased induction level of the biosensor at the time of cell collection influenced the fermentation performance, an automated control system was devised. This system utilised data from the flow cytometry analysis to control the level of inhibitors in the cultivation feed. Consequently, when the biosensor signal began to decline, higher amounts of inhibitors were added, as long as the addition did not lead to an increase in the number of damaged cells.A second biosensor was used in this thesis work to investigate the sugar signalling response of S. cerevisiae to the presence of xylose. Xylose is the second most abundant sugar in lignocellulosic biomass; however, naturally, S. cerevisiae cannot metabolise it. Genetically modified S. cerevisiae strains have been generated by introducing heterologous pathways such as the XR/XDH or XI pathways to enable xylose consumption. Nevertheless, xylose consumption rates remain lower compared to glucose. Sugar signalling emerged as a potential bottleneck in the efficient utilisation of xylose. In the present work, the response of the SUC2p-yEGFP biosensor for sugar signalling was found to vary significantly depending on the pathway employed. A higher induction for the strains carrying the XI pathway was associated with poorer growth on xylose. Lastly, the effect of introducing a xylose epimerase capable of catalysing the conversion between the two anomers, α-D-xylopyranose and β-D-xylopyranose, as a strategy to improve xylose consumption was studied. The effect was enzyme-specific and proved to be particularly beneficial in strains utilising the xylose isomerase from Lachnoclostridium phytofermentans.In conclusion, the results presented in this thesis demonstrate how biosensors can facilitate the understanding and monitoring of intracellular processes that occur within the cell under stress conditions and be a key tool for improving production processes.
  •  
32.
  • Kanagarajan, Selvaraju, et al. (författare)
  • Production of functional human fetal hemoglobin in Nicotiana benthamiana for development of hemoglobin-based oxygen carriers
  • 2021
  • Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 184, s. 955-966
  • Tidskriftsartikel (refereegranskat)abstract
    • Hemoglobin-based oxygen carriers have long been pursued to meet clinical needs by using native hemoglobin (Hb) from human or animal blood, or recombinantly produced Hb, but the development has been impeded by safety and toxicity issues. Herewith we report the successful production of human fetal hemoglobin (HbF) in Nicotiana benthamiana through Agrobacterium tumefaciens-mediated transient expression. HbF is a heterotetrameric protein composed of two identical α- and two identical γ-subunits, held together by hydrophobic interactions, hydrogen bonds, and salt bridges. In our study, the α- and γ-subunits of HbF were fused in order to stabilize the α-subunits and facilitate balanced expression of α- and γ-subunits in N. benthamiana. Efficient extraction and purification methods enabled production of the recombinantly fused endotoxin-free HbF (rfHbF) in high quantity and quality. The transiently expressed rfHbF protein was identified by SDS-PAGE, Western blot and liquid chromatography-tandem mass spectrometry analyses. The purified rfHbF possessed structural and functional properties similar to native HbF, which were confirmed by biophysical, biochemical, and in vivo animal studies. The results demonstrate a high potential of plant expression systems in producing Hb products for use as blood substitutes.
  •  
33.
  • Janssen, Mathias, 1973, et al. (författare)
  • Life cycle impacts of ethanol production from spruce wood chips under high gravity conditions
  • 2016
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 9:1, s. 53-
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundDevelopment of more sustainable biofuel production processes is ongoing, and technology to run these processes at a high dry matter content, also called high-gravity conditions, is one option. This paper presents the results of a life cycle assessment (LCA) of such a technology currently in development for the production of bio-ethanol from spruce wood chips.ResultsThe cradle-to-gate LCA used lab results from a set of 30 experiments (or process configurations) in which the main process variable was the detoxification strategy applied to the pretreated feedstock material. The results of the assessment show that a process configuration, in which washing of the pretreated slurry is the detoxification strategy, leads to the lowest environmental impact of the process. Enzyme production and use are the main contributors to the environmental impact in all process configurations, and strategies to significantly reduce this contribution are enzyme recycling and on-site enzyme production. Furthermore, a strong linear correlation between the ethanol yield of a configuration and its environmental impact is demonstrated, and the selected environmental impacts show a very strong cross-correlation (r^2 > 0.9 in all cases) which may be used to reduce the number of impact categories considered from four to one (in this case, global warming potential). Lastly, a comparison with results of an LCA of ethanol production under high-gravity conditions using wheat straw shows that the environmental performance does not significantly differ when using spruce wood chips. For this comparison, it is shown that eutrophication potential also needs to be considered due to the fertilizer use in wheat cultivation.ConclusionsThe LCA points out the environmental hotspots in the ethanol production process, and thus provides input to the further development of the high-gravity technology. Reducing the number of impact categories based only on cross-correlations should be done with caution. Knowledge of the analyzed system provides further input to the choice of impact categories.
  •  
34.
  • Jers, C., et al. (författare)
  • Production of 3-hydroxypropanoic acid from glycerol by metabolically engineered bacteria
  • 2019
  • Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 7:MAY
  • Forskningsöversikt (refereegranskat)abstract
    • 3-hydroxypropanoic acid (3-HP) is a valuable platform chemical with a high demand in the global market. 3-HP can be produced from various renewable resources. It is used as a precursor in industrial production of a number of chemicals, such as acrylic acid and its many derivatives. In its polymerized form, 3-HP can be used in bioplastic production. Several microbes naturally possess the biosynthetic pathways for production of 3-HP, and a number of these pathways have been introduced in some widely used cell factories, such as Escherichia coli and Saccharomyces cerevisiae. Latest advances in the field of metabolic engineering and synthetic biology have led to more efficient methods for bio-production of 3-HP. These include new approaches for introducing heterologous pathways, precise control of gene expression, rational enzyme engineering, redirecting the carbon flux based on in silico predictions using genome scale metabolic models, as well as optimizing fermentation conditions. Despite the fact that the production of 3-HP has been extensively explored in established industrially relevant cell factories, the current production processes have not yet reached the levels required for industrial exploitation. In this review, we explore the state of the art in 3-HP bio-production, comparing the yields and titers achieved in different microbial cell factories and we discuss possible methodologies that could make the final step toward industrially relevant cell factories.
  •  
35.
  • Harirchi, S., et al. (författare)
  • Efficacy of polyextremophilic Aeribacillus pallidus on bioprocessing of beet vinasse derived from ethanol industries
  • 2020
  • Ingår i: Bioresource Technology. - : Elsevier Ltd. - 0960-8524 .- 1873-2976. ; 313
  • Tidskriftsartikel (refereegranskat)abstract
    • This work aimed to evaluate the applicability of Aeribacillus pallidus for the aerobic treatment of the concentrated beet vinasse with high chemical oxygen demand (COD 685 g.L−1) that is defined as an environmental pollutant. This bacterium is a polyextremophilic strain and grow aerobically up to 7.5% vinasse at high temperature (50 °C). In the bioreactor and under controlled conditions, A. pallidus reduced the soluble COD content of 5% vinasse up to 27% during 48 h and utilized glucose and glycerol, completely. Furthermore, a reduction of manganese, copper, aluminum, and nickel concentrations was observed in the treated vinasse with A. pallidus. The obtained results make this strain as an appropriate alternative to be used for the aerobic bioprocessing of the vinasse. © 2020 The Author(s)
  •  
36.
  • Olsson, Lisbeth, 1963, et al. (författare)
  • Microbial robustness in bioprocesses
  • 2023
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Yeast is broadly exploited for industrial use, and strains are constantly improved to meet the requirements to produce the targeted product with high yield, productivity and titer. Successful strains have consistent performance also in presence of different perturbations, i.e. their performance is robust. The concept of microbial robustness will be discussed and contrasted to tolerance toward specific stresses. Furthermore, a method to quantitatively assess microbial robustness will be presented. This method allows a high throughput evaluation, in a perturbation space where different cellular function can form the basis for the evaluation. Another important tool box to examine intracellular status in face of pertubations are biosensors. Examples of applying these two methodologies towards microbial robustness will be discussed. We have used the tools to scale down bioprocesses and their perturbation, to follow adaptive laboratory evolution and to gain understanding of subpopulations.
  •  
37.
  • Tang, Hongting, et al. (författare)
  • Efficient yeast surface-display of novel complex synthetic cellulosomes
  • 2018
  • Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 17:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The self-assembly of cellulosomes on the surface of yeast is a promising strategy for consolidated bioprocessing to convert cellulose into ethanol in one step. Results: In this study, we developed a novel synthetic cellulosome that anchors to the endogenous yeast cell wall protein a-agglutinin through disulfide bonds. A synthetic scaffoldin ScafAGA3 was constructed using the repeated N-terminus of Aga1p and displayed on the yeast cell surface. Secreted cellulases were then fused with Aga2p to assemble the cellulosome. The display efficiency of the synthetic scaffoldin and the assembly efficiency of each enzyme were much higher than those of the most frequently constructed cellulosome using scaffoldin ScafCipA3 from Clostridium thermocellum. A complex cellulosome with two scaffoldins was also constructed using interactions between the displayed anchoring scaffoldin ScafAGA3 and scaffoldin I ScafCipA3 through disulfide bonds, and the assembly of secreted cellulases to ScafCipA3. The newly designed cellulosomes enabled yeast to directly ferment cellulose into ethanol. Conclusions: This is the first report on the development of complex multiple-component assembly system through disulfide bonds. This strategy could facilitate the construction of yeast cell factories to express synergistic enzymes for use in biotechnology.
  •  
38.
  • Wang, Ruifei, 1985 (författare)
  • Bioprocess development for biochemical conversion of lignocellulose
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Due to its low environmental impact and high maturity of the fuel ethanol market, lignocellulosic ethanol is a promising option for reducing the carbon footprint in the transport sector. The characteristics of lignocellulosic feedstocks, such as varied sugar composition, low sugar density, low solubility, recalcitrance to enzymatic degradation, and inhibitors formed during thermochemical pretreatment, have so far limited the production process, and costs for conversion of lignocellulosic materials to ethanol are still high. In this thesis, I describe the development of a bioconversion process that pushes the limits of simultaneous saccharification and co-fermentation (SSCF) to achieve higher ethanol titre, yield and productivity on lignocellulosic feedstocks. I propose an integrated fed-batch strategy, Multi-Feed SSCF, including feeds of substrates, enzymes and adapted cells to tackle the technical challenges in operating a SSCF process at high substrate loadings. Using insights from experiments and a model-based feeding design, lignocellulose saccharification and fermentation at water insoluble solids (WIS) levels greater than 20% (w/w) was achieved. The multi-feed SSCF concept and model-aided substrate feeding design allowed rapid, reproducible, and scalable bioconversion of lignocellulose, as proven on several lignocellulosic feedstocks in both laboratory and demonstration scales. Ethanol production above 50 g/L in SSCF processes was found to be severely inhibited by the combined effects of ethanol, lignocellulose-derived inhibitors, and higher than standard cultivation temperature (35°C). Cell viability and fermentation improved significantly in a multi-feed SSCF process with a step change in temperature from 35 to 30°C, compared to operation at 35°C throughout. However, introducing the Erg3Tyr185 point mutation which has been reported to render thermotolerance in yeast, did not offer any significant improvement. Cell concentrations were determined by counting in a hemocytometer and colony forming unit assay. Their accuracy and reproducibility in lignocellulosic media, were verified by Design-of-Experiment-based calibration. Applic-ability of real time qPCR and dielectric spectroscopy as potential cell quantification methods was also investigated. With multi-feed of solid substrates, enzyme preparations, and adapted cells, the SSCF process produced > 60 g/L ethanol within 120 h, equivalent to 70% of the theoretical yield of the total sugar input, and 90% of the consumed sugar. The systematic optimisation reported in this work represents a robust and reproducible routine for developing lignocellulose-based processes. It could inspire continuous development of alternative strategies to current fossil-based chemical/fuel processes.
  •  
39.
  • Olsson, Lisbeth, 1963, et al. (författare)
  • Robustness: linking strain design to viable bioprocesses
  • 2022
  • Ingår i: Trends in Biotechnology. - : Elsevier BV. - 0167-7799 .- 1879-3096. ; 40:8, s. 918-931
  • Forskningsöversikt (refereegranskat)abstract
    • Microbial cell factories are becoming increasingly popular for the sustainable production of various chemicals. Metabolic engineering has led to the design of advanced cell factories; however, their long-term yield, titer, and productivity falter when scaled up and subjected to industrial conditions. This limitation arises from a lack of robustness – the ability to maintain a constant phenotype despite the perturbations of such processes. This review describes predictable and stochastic industrial perturbations as well as state-of-the-art technologies to counter process variability. Moreover, we distinguish robustness from tolerance and discuss the potential of single-cell studies for improving system robustness. Finally, we highlight ways of achieving consistent and comparable quantification of robustness that can guide the selection of strains for industrial bioprocesses.
  •  
40.
  • Bonander, Nicklas, 1968, et al. (författare)
  • Optimizing yeast as a host for recombinant protein production
  • 2011
  • Bok (övrigt vetenskapligt/konstnärligt)abstract
    • Having access to suitably stable, functional recombinant protein samples underpins diverse academic and industrial research efforts to understand the workings of the cell in health and disease. Synthesizing a protein in recombinant host cells typically allows the isolation of the pure protein in quantities much higher than those found in the protein's native source. Yeast is a popular host as it is a eukaryote with similar synthetic machinery to the native human source cells of many proteins of interest, whilst also being quick, easy and cheap to grow and process. Even in these cells the production of some proteins can be plagued by low functional yields. We have identified molecular mechanisms and culture parameters underpinning high yields and have consolidated our findings to engineer improved yeast cell factories. In this chapter we provide an overview of the opportunities available to improve yeast as a host system for recombinant protein production.
  •  
41.
  • Aulitto, Martina, 1991, et al. (författare)
  • Seed culture pre-adaptation of Bacillus coagulans MA-13 improves lactic acid production in simultaneous saccharification and fermentation
  • 2019
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Lignocellulosic biomass is an abundant and sustainable feedstock, which represents a promising raw material for the production of lactic acid via microbial fermentation. However, toxic compounds that affect microbial growth and metabolism are released from the biomass upon thermochemical pre-treatment. So far, susceptibility of bacterial strains to biomass-derived inhibitors still represents a major barrier to lactic acid production from lignocellulose. Detoxification of the pre-treated lignocellulosic material by water washing is commonly performed to alleviate growth inhibition of the production microorganism and achieve higher production rates. Results In this study, we assessed the feasibility of replacing the washing step with integrated cellular adaptation during pre-culture of Bacillus coagulans MA-13 prior to simultaneous saccharification and lactic acid fermentation of steam exploded wheat straw. Using a seed culture pre-exposed to 30% hydrolysate led to 50% shorter process time, 50% higher average volumetric and 115% higher average specific productivity than when using cells from a hydrolysate-free seed culture. Conclusions Pre-exposure of B. coagulans MA-13 to hydrolysate supports adaptation to the actual production medium. This strategy leads to lower process water requirements and combines cost-effective seed cultivation with physiological pre-adaptation of the production strain, resulting in reduced lactic acid production costs.
  •  
42.
  • Muraleedharan, Madhu Nair, et al. (författare)
  • Isolation and modification of nano-scale cellulose from organosolv-treated birch through the synergistic activity of LPMO and endoglucanases
  • 2021
  • Ingår i: International Journal of Biological Macromolecules. - : Elsevier. - 0141-8130 .- 1879-0003. ; 183, s. 101-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanocellulose isolation from lignocellulose is a tedious and expensive process with high energy and harsh chemical requirements, primarily due to the recalcitrance of the substrate, which otherwise would have been cost-effective due to its abundance. Replacing the chemical steps with biocatalytic processes offers opportunities to solve this bottleneck to a certain extent due to the enzymes substrate specificity and mild reaction chemistry. In this work, we demonstrate the isolation of sulphate-free nanocellulose from organosolv pretreated birch biomass using different glycosyl-hydrolases, along with accessory oxidative enzymes including a lytic polysaccharide monooxygenase (LPMO). The suggested process produced colloidal nanocellulose suspensions (ζ-potential −19.4 mV) with particles of 7–20 nm diameter, high carboxylate content and improved thermostability (To = 301 °C, Tmax = 337 °C). Nanocelluloses were subjected to post-modification using LPMOs of different regioselectivity. The sample from chemical route was the least favorable for LPMO to enhance the carboxylate content, while that from the C1-specific LPMO treatment showed the highest increase in carboxylate content.
  •  
43.
  • Nilsson, Robert, et al. (författare)
  • Techno-economics of carbon preserving butanol production using a combined fermentative and catalytic approach
  • 2014
  • Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 161, s. 263-269
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents a novel process for n-butanol production which combines a fermentation consuming carbon dioxide (succinic acid fermentation) with subsequent catalytic reduction steps to add hydrogen to form butanol. Process simulations in Aspen Plus have been the basis for the techno-economic analyses performed. The overall economy for the novel process cannot be justified, as production of succinic acid by fermentation is too costly. Though, succinic acid price is expected to drop drastically in a near future. By fully integrating the succinic acid fermentation with the catalytic conversion the need for costly recovery operations could be reduced. The hybrid process would need 22% less raw material than the butanol fermentation at a succinic acid fermentation yield of 0.7 g/g substrate. Additionally, a carbon dioxide fixation of up to 13 ktonnes could be achieved at a plant with an annual butanol production of 10 ktonnes
  •  
44.
  •  
45.
  • Antonopoulou, Io, 1989- (författare)
  • Development of biocatalytic processes for selective antioxidant production
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Feruloyl esterases (FAEs, EC 3.1.1.73) represent a subclass of carboxylic acid esterases that under normal conditions catalyze the hydrolysis of the ester bond between hydroxycinnamic acids (ferulic acid, sinapic acid, caffeic acid, p-coumaric acid) and sugar residues in plant cell walls. Based on their specificity towards monoferulates and diferulates, substitutions on the phenolic ring and on their amino acid sequence identity, they have been classified into four types (A-D) while phylogenetic analysis has resulted in classification into thirteen subfamilies (SF1-13). Under low water content, these enzymes are able to catalyze the esterification of hydroxycinnamic acids or the transesterification of their esters (donor) with alcohols or sugars (acceptor) resulting in compounds with modified lipophilicity, having a great potential for use in the tailor-made modification of natural antioxidants for cosmetic, cosmeceutical and pharmaceutical industries. The work described in this thesis focused on the selection,characterization and application of FAEs for the synthesis of bioactive esters with antioxidant activity in non-conventional media. The basis of the current classification systems was investigated in relation with the enzymes’ synthetic and hydrolytic abilities while the developed processes were evaluated for their efficiency and sustainability.Paper I was dedicated to the screening and evaluation of the synthetic abilities of 28 fungal FAEs using acceptors of different lipophilicity at fixed conditions in detergentless microemulsions. It was revealed that FAEs classified in phylogenetic subfamilies related to acetyl xylan esterases (SF5 and 6) showed increased transesterification rates and selectivity. In general, FAEs showed preference on more hydrophilic alcohol acceptors and in descending order to glycerol > 1-butanol > prenol. Homology modeling and small molecule docking simulations were employed as tools for the identification of a potential relationship between the predicted surface and active site properties of selected FAEs and the transesterification selectivity.Papers II- IV focused on the characterization of eight promising FAEs and the optimization of reaction conditions for the synthesis of two bioactive esters (prenyl ferulate and L-arabinose ferulate) in detergentless microemulsions. The effect of the medium composition, the donor and acceptor concentration, the enzyme load, the pH, the temperature and the agitation on the transesterification yield and selectivity were investigated. It was observed that the acceptor concentration and enzyme load were crucial parameters for selectivity. Fae125 (Type A, SF5) iiexhibited highest prenyl ferulate yield (81.1%) and selectivity (4.685) converting 98.5% of VFA to products after optimization at 60 mM VFA, 1.5 M prenol, 0.04 mg FAE mL-1, 40oC, 24 h, 53.4:43.4:3.2 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0. On the other hand, FaeA1 (Type A, SF5) showed highest L-arabinose ferulate yield (52.2 %) and selectivity (1.120) at 80 mM VFA, 55 mM L-arabinose, 0.02 mg FAE mL-1, 50oC, 8 h, 19.8: 74.7: 5.5 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0.In paper V, the effect of reaction media on the enzyme stability and transesterification yield and selectivity was studied in different solvents for the synthesis of two bioactive esters: prenyl ferulate and L-arabinose ferulate. The best performing enzyme (Fae125) was used in the optimization of reaction conditions in the best solvent (n-hexane) via response surface methodology. Both bioconversions were best described by a two-factor interaction model while optimal conditions were determined as the ones resulting in highest yield and selectivity.Highest prenyl ferulate yield (87.5%) and selectivity (7.616) were observed at 18.56 mM prenol mM-1VFA, 0.04 mg FAE mL-1, 24.5 oC, 24.5 h, 91.8: 8.2 v/v n-hexane: 100 mM sodium acetate pH 4.7. Highest L-arabinose ferulate yield (56.2%) and selectivity (1.284) were observed at 2.96 mM L-arabinose mM-1VFA, 0.02 mg FAE mL-1, 38.9 oC, 12 h, 90.5: 5.0: 4.5 v/v/v n-hexane: dimethyl sulfoxide: 100 mM sodium acetate pH 4.7. The enzyme could be reused for six consecutive reaction cycles maintaining 66.6% of its initial synthetic activity. The developed bioconversions showed exceptional biocatalyst productivities (> 300 g product g-1FAE) and the waste production was within the range of pharmaceutical processes.Paper VI focused on the investigation of the basis of the type A classification of a well-studied FAE from Aspergillus niger(AnFaeA) by comparing its activity towards methyl and arabinose hydroxycinnamic acid esters. For this purpose, L-arabinose ferulateand caffeate were synthesized enzymatically. kcat/Kmratios revealed that AnFaeA hydrolyzed arabinose ferulate 1600 times and arabinose caffeate 6.5 times more efficiently than methyl esters. This study demonstrated that short alkyl chain hydroxycinnamate esters which are used nowadays for FAE classification can lead to activity misclassification, while L-arabinose esters could potentially substitute synthetic esters in classification describing more adequately the enzyme specificitiesin the natural environment.
  •  
46.
  • Faisal, Abrar, et al. (författare)
  • Recovery of l-Arginine from Model Solutions and Fermentation Broth Using Zeolite-Y Adsorbent
  • 2019
  • Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:9, s. 8900-8907
  • Tidskriftsartikel (refereegranskat)abstract
    • Arginine was produced via fermentation of sugars using the engineered microorganism Escherichia coli. Zeolite-Y adsorbents in the form of powder and extrudates were used to recover arginine from both a real fermentation broth and aqueous model solutions. An adsorption isotherm was determined using model solutions and zeolite-Y powder. The saturation loading was determined to be 0.2 g/g using the Sips model. Arginine adsorbed from a real fermentation broth using either zeolite-Y powder or extrudates both showed a maximum loading of 0.15 g/g at pH 11. This adsorbed loading is very close to the corresponding value obtained from the model solution showing that under the experimental conditions the presence of additional components in the broth did not have a significant effect on the adsorption of arginine. Furthermore, a breakthrough curve was determined for extrudates using a 1 wt % arginine model solution. The selectivity for arginine over ammonia and alanine from the real fermentation broth at pH 11 was 1.9 and 8.3, respectively, for powder, and 1.0, and 4.1, respectively, for extrudates. To the best of our knowledge, this is the first time recovery of arginine from real fermentation broths using any type of adsorbent has been reported.
  •  
47.
  • Mukesh Kumar, Awasthi, et al. (författare)
  • Bacterial dynamics during the anaerobic digestion of toxic citrus fruit waste and semi-continues volatile fatty acids production in membrane bioreactors
  • 2022
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 319
  • Tidskriftsartikel (refereegranskat)abstract
    • Citrus wastes (CW) are normally toxic to anaerobic digestion (AD) because of flavors such as D-limonene. In this study, bacterial community was evaluated during volatile fatty acids (VFAs) production from CW inoculated by sludge in a membrane bioreactor (MBR) using semi-continuous AD with different organic loading rates (OLR). Four treatments including untreated CW filled with 4 and 8 g center dot VS center dot L(-1)d(-1) OLR (UOLR4 and UOLR8), pretreated Dlimonene-free CW filled with 4 and 8 g center dot VS center dot L(-1)d(-1) OLR (POLR4 and POLR8). The initial inoculum and the CW mixture (DAY0) was used as control for comparison. There was an obviously higher bacterial diversity in raw material (66848 sequences in DAY0), while decreased after AD and higher in POLR4 and POLR8 (65239 and 63916) than UOLR4 and UOLR8 (49158 and 51936). The key bacterial associated with VFAs production mainly affiliated to Firmicutes (37.35-84.73%), Bacteroidetes (0.48-36.87%), and Actinobacteria (0.35-29.38%), and the key genus composed of Lactobacillus, Prevotella, Bacillus, Bacteroides and Olsenella which contributed in VFA generation by degradable complex organic compounds. Noticeably, methanogen completely suppressed after MBR-AD and UOLR4 has greater acid utilizing bacteria (70.09%).
  •  
48.
  • Helstad, Amanda, et al. (författare)
  • Protein extraction from cold-pressed hempseed press cake: From laboratory to pilot scale
  • 2022
  • Ingår i: Journal of Food Science. - : Wiley. - 1750-3841 .- 0022-1147. ; 87:1, s. 312-325
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract: During the production of industrial hempseed oil, a press cake is formed as a byproduct, which is often used as animal feed although it contains a high amount of protein that could be used for human consumption. Extracting this valuable protein would reduce food waste and increase the availability of plant-based protein. A protein extraction process based on the pH-shift method was adapted to improve the protein extraction yield from industrial hempseed press cake (HPC). Parameters such as alkali extraction pH, time, and temperature, as well as isoelectric precipitation pH, were investigated in laboratory scale and were thereafter carried out in a pilot trial to explore the suitability for future scale up. The phytic acid content of the extracted protein isolate was also analyzed to investigate any potential inhibitory effect on mineral absorption. A final protein yield of 60.6%, with a precipitated protein content of 90.3% (dw), was obtained using a constant alkali extraction pH of 10.5 for 1 h at room temperature, followed by precipitation at pH 5.5. The pilot trial showed promising results for the future production of industrial hemp protein precipitate on a larger scale, showing a protein yield of 57.0% and protein content of 90.8% (dw). The amount of phytic acid in the protein isolate produced in the optimal laboratory experiment and in the pilot trial was 0.595 and 0.557 g phytic acid/100 g dw, respectively, which is 83%–88% less than in the HPC. This is in the range of other plant-based protein sources (tofu, kidney beans, peas, etc.). Practical Application: Industrial hempseed press cake is a byproduct in the production of industrial hempseed oil, which is mostly used as animal feed, but has the potential to become an additional source of plant-based protein for human consumption with a suitable protein extraction method. The extracted hemp protein could be used to develop new plant-based dairy or meat analog products.
  •  
49.
  •  
50.
  • Nielsen, Fredrik (författare)
  • Process development for combined pentose and hexose fermentation
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Second-generation ethanol from lignocellulose is a sustainable alternative that can partially replace fossil fuels. To be competitive with first generation ethanol from sugar and starch crops and fossil fuels, the conversion efficiency and ethanol yields of second-generation ethanol conversion processes must be improved. Improving the performance of the fermenting microorganism and efficiently convert both glucose and xylose in lignocellulosic biomass is imperative to achieve these targets. This thesis addresses means to improve the performance of the biochemical steps of the lignocellulose-to-ethanol process. The main focus has been on enhancing the xylose utilization of xylose-fermenting Saccharomyces cerevisiae by adapting the yeast to lignocellulosic hydrolysates during propagation and developing novel co-fermentation strategies that promote xylose utilization. Co-fermentation strategies based on separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) were investigated.Furthermore, scale-up of co-fermentation strategies and the use of multiple and blended feedstocks in the conversion process were investigated. The findings show that adaptation of the yeast to the conditions in fermentation during propagation provides a broad adaptive response that improves fermentation performance of xylose-fermenting S. cerevisiae. Co-fermentation designs that take the xylose consumption patterns of xylose-fermenting S. cerevisiae into consideration can further enhance the xylose utilization and ethanol yields. Furthermore, feedstocks with similar attributes and blends thereof could be concurrently pretreated and co-fermented, eliciting comparable ethanol yields of the whole range of feedstocks and feedstock blends. This suggests that feedstocks with similar attributes can be used interchangeably to improve supply efficiency and hedge economic and technologic risks. Scale-up experiments show that the advanced co-fermentation strategies can be scaled-up from lab scale to process development and demonstration scale and maintain comparable ethanol yields, thus bringing the lab-scale process improvements closer to implementation at commercial scale.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 785
Typ av publikation
tidskriftsartikel (548)
konferensbidrag (78)
doktorsavhandling (47)
forskningsöversikt (39)
bokkapitel (26)
annan publikation (18)
visa fler...
licentiatavhandling (12)
rapport (5)
samlingsverk (redaktörskap) (4)
bok (4)
patent (4)
konstnärligt arbete (1)
visa färre...
Typ av innehåll
refereegranskat (635)
övrigt vetenskapligt/konstnärligt (140)
populärvet., debatt m.m. (10)
Författare/redaktör
Christakopoulos, Pau ... (184)
Rova, Ulrika (167)
Matsakas, Leonidas (110)
Berglund, Kris (81)
Topakas, Evangelos (58)
Hodge, David (45)
visa fler...
Patel, Alok, Dr. 198 ... (32)
Taherzadeh, Mohammad ... (31)
Olsson, Lisbeth, 196 ... (24)
Hodge, David B. (19)
Sjöblom, Magnus (16)
Enman, Josefine (16)
Albers, Eva, 1966 (15)
Hegg, Eric L. (15)
Antonopoulou, Io, 19 ... (14)
Chotteau, Véronique, ... (14)
Janssen, Mathias, 19 ... (13)
Karnaouri, Anthi C. (13)
Hrůzová, Kateřina (12)
Karnaouri, Anthi (12)
Andersson, Christian (11)
Mandenius, Carl-Fred ... (11)
Sarkar, Omprakash (11)
Zerva, Anastasia (11)
Dimarogona, Maria (11)
Mahboubi, Amir (10)
Chotteau, Véronique (10)
Franzén, Carl Johan, ... (10)
Helmerius, Jonas (10)
Hagander, Per (9)
Antonopoulou, Io (9)
Schwarz, Hubert (9)
Williams, Daniel L. (9)
Nielsen, Jens B, 196 ... (8)
Hatti-Kaul, Rajni (8)
Wallberg, Ola (8)
Mayers, Joshua, 1988 (8)
Jûtten, Peter (8)
Krige, Adolf (8)
Bhalla, Aditya (8)
Singh, Sandip K. (8)
Stoklosa, Ryan J. (8)
Li, Muyang (8)
Katsimpouras, Consta ... (8)
Lidén, Gunnar (7)
Holst, Olle (7)
Mattiasson, Bo (7)
Sandgren, Mats (7)
Martin, Carlos (7)
Muraleedharan, Madhu ... (7)
visa färre...
Lärosäte
Luleå tekniska universitet (424)
Chalmers tekniska högskola (130)
Lunds universitet (91)
Kungliga Tekniska Högskolan (65)
Högskolan i Borås (41)
Sveriges Lantbruksuniversitet (36)
visa fler...
Umeå universitet (31)
Linköpings universitet (23)
RISE (19)
Göteborgs universitet (12)
Uppsala universitet (7)
Linnéuniversitetet (7)
Mälardalens universitet (6)
Stockholms universitet (4)
Karolinska Institutet (4)
Örebro universitet (3)
Mittuniversitetet (3)
Högskolan i Halmstad (1)
IVL Svenska Miljöinstitutet (1)
visa färre...
Språk
Engelska (784)
Tyska (1)
Forskningsämne (UKÄ/SCB)
Teknik (785)
Naturvetenskap (130)
Lantbruksvetenskap (26)
Medicin och hälsovetenskap (19)
Samhällsvetenskap (1)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy