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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.	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.
3.	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.
4.	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.
5.	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.
6.	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.
7.	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.
8.	Bettiga, Maurizio, 1978, et al. (författare) Robust S. cerevisiae strain for next generation bio-processes: concepts and case-studies 2013 Ingår i: Cell Factories and Biosustainability (Hilleroed, Denmark, May 5-8 2013). Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract The realization of an oil independent economy relies on the development of competitive processes for the production of fuels and chemicals from renewable resources. The extensive research on second-generation ethanol has paved the way to a new concept of bio-based industry, where lignocellulosic material is the primary source of sugars, to be converted to a number of fuels and chemicals. Harsh conditions during the bioconversion of lignocellulose-derived sugars to the desired products drastically hamper cell viability and therefore productivity. Microbial inhibition limits bioprocesses to an extent such that it can be said that understanding and harnessing microbial robustness is a prerequisite for the feasibility of new bioprocess and the production of renewable fuels and chemicals.Current research carried out by our group focuses on the yeast Saccharomyces cerevisiae and aims at investigating the molecular bases of microbial robustness. Our efforts include the identification of the molecular targets of different classes of fermentation inhibitors aiming at understanding the complex responses of the cells to these compounds. The final goal is to engineer more robust strains. The concept of robustness will be discussed and examples of key features for S. cerevisiae robustness as well as examples of successful engineering to increase robustness will be presented.
9.	Bettiga, Maurizio, 1978, et al. (författare) Robust S. cerevisiae strain for next generation bio-processes: concepts and case-studies 2013 Ingår i: 35th Symposium on Biotechnology for Fuels and Chemicals (Portland, OR. April 29-May 2, 2013). Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract The realization of an oil independent economy relies on the development of competitive processes for the production of fuels and chemicals from renewable resources. The extensive research on second-generation ethanol has paved the way to a new concept of bio-based industry, where lignocellulosic material is the primary source of sugars, to be converted to a number of fuels and chemicals. Sugars are released from cellulose and hemicellulose by pretreatment and hydrolysis steps. Harsh conditions result in the formation of a number of compounds, originating from sugars and lignin breakdown and acting as microorganism inhibitors. Weak organic acids, furaldehydes and phenolic compounds are sources of stress for the fermenting microorganism, as they influence cellular metabolism in a number of ways, including direct damage on cellular functions or by perturbations of the cellular energy and redox metabolism. In addition, the product of interest can act as a potent inhibitor. Regardless of the product, robust microorganisms are a prerequisite for the feasibility of lignocellulose-based bioprocesses.Current research carried out by our group focuses on the yeast Saccharomyces cerevisiae and aims at investigating the molecular bases of microbial robustness. Our efforts include the identification of the molecular targets of different classes of fermentation inhibitors aiming at understanding the complex responses of the cells to these compounds. The final goal is to engineer more robust strains. The concept of robustness will be discussed and examples of key features for S. cerevisiae robustness as well as examples of successful engineering to increase robustness will be presented.
10.	Nygård, Yvonne, 1986 (författare) Synthetic Biology and Metabolic Engineering for Future Biorefineries 2017 Ingår i: Bioprocessing India, Guwahati 2017. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
11.	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.
12.	Svensson, Sofie, et al. (författare) Fungal textiles : Wet spinning of fungal microfibers to produce monofilament yarns 2021 Ingår i: Sustainable Materials and Technologies. - : Elsevier BV. - 2214-9937. ; 28 Tidskriftsartikel (refereegranskat)abstract The cell wall of a zygomycetes fungus was successfully wet spun into monofilament yarns and demonstrated as a novel resource for production of sustainable textiles. Furthermore, the fungus could be cultivated on bread waste, an abundant food waste with large negative environmental impact if not further utilized. Rhizopus delemar was first cultivated in bread waste in a bubble column bioreactor. The fungal cell wall collected through alkali treatment of fungal biomass contained 36 and 23% glucosamine and N-acetyl glucosamine representing chitosan and chitin in the cell wall, respectively. The amino groups of chitosan were protonated by utilizing acetic or lactic acid. This resulted in the formation of a uniform hydrogel of fungal microfibers. The obtained hydrogel was wet spun into an ethanol coagulation bath to form an aggregated monofilament, which was finally dried. SEM images confirmed the alignment of fungal microfibers along the monofilament axis. The wet spun monofilaments had tensile strengths up to 69.5 MPa and Young's modulus of 4.97 GPa. This work demonstrates an environmentally benign procedure to fabricate renewable fibers from fungal cell wall cultivated on abundant food waste, which opens a window to creation of sustainable fungal textiles.
13.	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.
14.	Westman, Johan (författare) Ethanol production from lignocellulose using high local cell density yeast cultures. Investigations of flocculating and encapsulated Saccharomyces cerevisiae 2014 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Efforts are made to change from 1st to 2nd generation bioethanol production, using lignocellulosics as raw materials rather than using raw materials that alternatively can be used as food sources. An issue with lignocellulosics is that a harsh pretreatment step is required in the process of converting them into fermentable sugars. In this step, inhibitory compounds such as furan aldehydes and carboxylic acids are formed, leading to suboptimal fermentation rates. Another issue is that lignocellulosics may contain a large portion of pentoses, which cannot be fermented simultaneously with glucose by Saccharomyces cerevisiae. In this thesis, high local cell density has been investigated as a means of overcoming these two issues. Encapsulation of yeast in semi-permeable alginate-chitosan capsules increased the tolerance towards furan aldehydes, but not towards carboxylic acids. The selective tolerance can be explained by differences in the concentration of compounds radially through the cell pellet inside the capsule. For inhibitors, gradients will only be formed if the compounds are readily convertible, like the furan aldehydes. Conversion of inhibitors by cells close to the membrane leads to decreased concentrations radially through the cell pellet. Thus, cells closer to the core experience subinhibitory levels of inhibitors and can ferment sugars. Carbohydrate gradients also give rise to nutrient limitations, which in turn trigger a stress response in the yeast, as was observed on mRNA and protein level. The stress response is believed to increase the robustness of the yeast and lead to improved tolerance towards additional stress. Glucose and xylose co-consumption by a recombinant strain, CEN.PK XXX, was also improved by encapsulation. Differences in affinity of the sugar transporters normally result in that glucose is taken up preferentially to xylose. However, when encapsulated, cells in different parts of the capsule experienced high and low glucose concentrations simultaneously. Xylose and glucose could thus be taken up concurrently. This improved the co-utilisation of the sugars by the system and led to 50% higher xylose consumption and 15% higher final ethanol titres. A protective effect by the capsule membrane itself could not be shown. Hence, the interest in flocculation was triggered, as a more convenient way to keep the cells together. To investigate whether flocculation increases the tolerance, like encapsulation, recombinant flocculating yeast strains were constructed and compared with the non-flocculating parental strain. Experiments showed that strong flocculation did not increase the tolerance towards carboxylic acids. However, the tolerance towards a spruce hydrolysate and especially against furfural was indeed increased. The results of this thesis show that high local cell density yeast cultures have the potential to aid against two of the major problems for 2nd generation bioethanol production: inhibitors and simultaneous hexose and pentose utilisation.
15.	Gontia, Paul, 1984, et al. (författare) Life cycle assessment of bio-based sodium polyacrylate production from pulp mill side streams: Case study of thermo-mechanical and sulfite pulp mills 2016 Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 131, s. 475-484 Tidskriftsartikel (refereegranskat)abstract Sodium polyacrylate (Na-PA) is a super absorbent polymer, which is commonly used in diverse hygiene products. The polymer is currently produced from fossil feedstock and its production consequently leads to adverse environmental impacts. Na-PA production from sugars present in pulp mill side streams can potentially be a successful way to achieve a more sustainable production of this polymer. In order to guide the development of a novel biochemical process for producing Na-PA, a life cycle assessment was done in which Na-PA produced from side streams of thermo-mechanical pulp (TMP) and sulfite pulp mills were compared. Furthermore, a comparison was made with Na-PA produced from fossil resources. The results show that the main determinant of the environmental impact of the bio-based Na-PA production is the free sugar content in the side streams. The lowest environmental impact is achieved by the least diluted side streams. More diluted side streams require larger amounts of energy for concentration, and, if the diluted streams are not concentrated, processes such as hydrolysis and detoxification, and fermentation are the environmental hotspots. Furthermore, the higher the yield of the fermentation process, the lower the environmental impact will be. Lastly, the production of bio-based Na-PA led to a lower global warming potential for some of the considered pulp mill side streams, but all of the other impacts considered were higher, when compared to fossil-based Na-PA production. Therefore, in parallel with efforts to develop a high-yield yeast for the fermentation process, technology developers should focus on low energy concentration processes for the side streams.
16.	Karlsson, Emma, 1983, et al. (författare) In silico and in vitro studies of the reduction of unsaturated α,β bonds of trans-2-hexenedioic acid and 6-amino-trans-2-hexenoic acid – Important steps towards biobased production of adipic acid 2018 Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 13:2 Tidskriftsartikel (refereegranskat)abstract The biobased production of adipic acid, a precursor in the production of nylon, is of great interest in order to replace the current petrochemical production route. Glucose-rich lignocel-lulosic raw materials have high potential to replace the petrochemical raw material. A number of metabolic pathways have been proposed for the microbial conversion of glucose to adipic acid, but achieved yields and titers remain to be improved before industrial applications are feasible. One proposed pathway starts with lysine, an essential metabolite industrially produced from glucose by microorganisms. However, the drawback of this pathway is that several reactions are involved where there is no known efficient enzyme. By changing the order of the enzymatic reactions, we were able to identify an alternative pathway with one unknown enzyme less compared to the original pathway. One of the reactions lacking known enzymes is the reduction of the unsaturated α,β bond of 6-amino-trans-2-hexenoic acid and trans-2hexenedioic acid. To identify the necessary enzymes, we selected N-ethylmaleimide reductase from Escherichia coli and Old Yellow Enzyme 1 from Saccharomyces pastorianus. Despite successful in silico docking studies, where both target substrates could fit in the enzyme pockets, and hydrogen bonds with catalytic residues of both enzymes were predicted, no in vitro activity was observed. We hypothesize that the lack of activity is due to a difference in electron withdrawing potential between the naturally reduced aldehyde and the carboxylate groups of our target substrates. Suggestions for protein engineering to induce the reactions are discussed, as well as the advantages and disadvantages of the two metabolic pathways from lysine. We have highlighted bottlenecks associated with the lysine pathways, and proposed ways of addressing them.
17.	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%).
18.	Gullfot, Fredrika, 1967- (författare) Synthesis of xyloglucan oligo- and polysaccharides with glycosynthase technology 2009 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Xyloglucans are polysaccharides found as storage polymers in seeds and tubers, and as cross-linking glycans in the cell wall of plants. Their structure is complex with intricate branching patterns, which contribute to the physical properties of the polysaccharide including its binding to and interaction with other glycans such as cellulose. Xyloglucan is widely used in bulk quantities in the food, textile and paper making industries. With an increasing interest in technically more advanced applications of xyloglucan, such as novel biocomposites, there is a need to understand and control the properties and interactions of xyloglucan with other compounds, to decipher the relationship between xyloglucan structure and function, and in particular the effect of different branching patterns. However, due to the structural heterogeneity of the polysaccharide as obtained from natural sources, relevant studies have not been possible to perform in practise. This fact has stimulated an interest in synthetic methods to obtain xyloglucan mimics and analogs with well-defined structure and decoration patterns. Glycosynthases are hydrolytically inactive mutant glycosidases that catalyse the formation of glycosidic linkages between glycosyl fluoride donors and glycoside acceptors. Since its first conception in 1998, the technology is emerging as a useful tool in the synthesis of large, complex polysaccharides. This thesis presents the generation and characterisation of glycosynthases based on xyloglucanase scaffolds for the synthesis of well-defined homogenous xyloglucan oligo- and polysaccharides with regular substitution patterns.
19.	Hong, Kuk-ki, 1976, et al. (författare) Metabolic Engineering of Saccharomyces cerevisiae: A Key Cell Factory Platform for Future Biorefineries 2012 Ingår i: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-9071 .- 1420-682X. ; 69:16, s. 2671-2690 Forskningsöversikt (refereegranskat)abstract Metabolic engineering is the enabling science of development of efficient cell factories for the production of fuels, chemicals, pharmaceuticals, and food ingredients through microbial fermentations. The yeast Saccharomyces cerevisiae is a key cell factory already used for the production of a wide range of industrial products, and here we review ongoing work, particularly in industry, on using this organism for the production of butanol, which can be used as biofuel, and isoprenoids, which can find a wide range of applications including as pharmaceuticals and as biodiesel. We also look into how engineering of yeast can lead to improved uptake of sugars that are present in biomass hydrolyzates, and hereby allow for utilization of biomass as feedstock in the production of fuels and chemicals employing S. cerevisiae. Finally, we discuss the perspectives of how technologies from systems biology and synthetic biology can be used to advance metabolic engineering of yeast.
20.	Sunner, Hampus, 1981, et al. (författare) Fungal Ferulic Acid Esterases – Specificity and Phylogeny 2009 Ingår i: Italic5 Science and Technology of Biomasses Proceedings Book, M Orlandi, C Crestine (Ed.). Italic5/COST conference, Sept 1-4 2009, Varenna, Italy. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Ferulic Acid Esterases (FAE) is a large heterogeneous group of enzymes with activity on esters of hydroxy- and metoxy- substituted cinnamic acid derivatives, such as ferulic acid. These ester bonds occur in the cell walls of plants and are especially common in grasses. As little systematic knowledge has been collected about this group of enzymes and only a few enzymes have been biochemically characterised to date, we have explored the phylogeny of FAEs using bioinformatic tools. We can conclude that the known Ferulic Acid Esterases belong to several evolutionary distant groups, two of which have dozens of highly related sequences, and a few groups with no members other than the known enzyme. The phylogeny also suggests certain similarities of substrate specificity within groups and proposes enzymes, whose biochemical characterisation would be especially informative for our understanding of the FAE families.
21.	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.
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.	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.
24.	van Dijk, Marlous, 1990, et al. (författare) Strain-dependent variance in short-term adaptation effects of two xylose-fermenting strains of Saccharomyces cerevisiae 2019 Ingår i: Bioresource technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 292, s. 121922- Tidskriftsartikel (refereegranskat)abstract The limited tolerance of Saccharomyces cerevisiae to the inhibitors present in lignocellulosic hydrolysates is a major challenge in second-generation bioethanol production. Short-term adaptation of the yeast to lignocellulosic hydrolysates during cell propagation has been shown to improve its tolerance, and thus its performance in lignocellulose fermentation. The aim of this study was to investigate the short-term adaptation effects in yeast strains with different genetic backgrounds. Fed-batch propagation cultures were supplemented with 40% wheat straw hydrolysate during the feed phase to adapt two different pentose-fermenting strains, CR01 and KE6-12. The harvested cells were used to inoculate fermentation media containing 80% or 90% wheat straw hydrolysate. The specific ethanol productivity during fermentation was up to 3.6 times higher for CR01 and 1.6 times higher for KE6-12 following adaptation. The influence of physiological parameters such as viability, storage carbohydrate content, and metabolite yields following short-term adaptation demonstrated that short-term adaptation was strain dependent.
25.	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.
26.	Abedinifar, S., et al. (författare) Ethanol production by Mucor indicus and Rhizopus oryzae from rice straw by separate hydrolysis and fermentation 2009 Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 33:5, s. 828-833 Tidskriftsartikel (refereegranskat)abstract Rice straw was successfully converted to ethanol by separate enzymatic hydrolysis and fermentation by Mucor indicus, Rhizopus oryzae, and Saccharomyces cerevisiae. The hydrolysis temperature and pH of commercial cellulase and β-glucosidase enzymes were first investigated and their best performance obtained at 45 °C and pH 5.0. The pretreatment of the straw with dilute-acid hydrolysis resulted in 0.72 g g-1 sugar yield during 48 h enzymatic hydrolysis, which was higher than steam-pretreated (0.60 g g-1) and untreated straw (0.46 g g-1). Furthermore, increasing the concentration of the dilute-acid pretreated straw from 20 to 50 and 100 g L-1 resulted in 13% and 16% lower sugar yield, respectively. Anaerobic cultivation of the hydrolyzates with M. indicus resulted in 0.36-0.43 g g-1 ethanol, 0.11-0.17 g g-1 biomass, and 0.04-0.06 g g-1 glycerol, which is comparable with the corresponding yields by S. cerevisiae (0.37-0.45 g g-1 ethanol, 0.04-0.10 g g-1 biomass and 0.05-0.07 glycerol). These two fungi produced no other major metabolite from the straw and completed the cultivation in less than 25 h. However, R. oryzae produced lactic acid as the major by-product with yield of 0.05-0.09 g g-1. This fungus had ethanol, biomass and glycerol yields of 0.33-0.41, 0.06-0.12, and 0.03-0.04 g g-1, respectively.
27.	Adeboye, Peter, 1982, et al. (författare) A coniferyl aldehyde dehydrogenase gene from Pseudomonas sp. strain HR199 enhances the conversion of coniferyl aldehyde by Saccharomyces cerevisiae 2016 Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 212:July 2016, s. 11-19 Tidskriftsartikel (refereegranskat)abstract AbstractThe conversion of coniferyl aldehyde to cinnamic acids by Saccharomyces cerevisiae under aerobic growth conditions was previously observed. Bacteria such as Pseudomonas have been shown to harbor specialized enzymes for converting coniferyl aldehyde but no comparable enzymes have been identified in S. cerevisiae. CALDH from Pseudomonas was expressed in S. cerevisiae. An acetaldehyde dehydrogenase (Ald5) was also hypothesized to be actively involved in the conversion of coniferyl aldehyde under aerobic growth conditions in S. cerevisiae. In a second S. cerevisiae strain, the acetaldehyde dehydrogenase (ALD5) was deleted. A prototrophic control strain was also engineered. The engineered S. cerevisiae strains were cultivated in the presence of 1.1 mM coniferyl aldehyde under aerobic condition in bioreactors. The results confirmed that expression of CALDH increased endogenous conversion of coniferyl aldehyde in S. cerevisiae and ALD5 is actively involved with the conversion of coniferyl aldehyde in S. cerevisiae.
28.	Albers, Eva, 1966, et al. (författare) Development and large scale performance of efficient xylose fermenting yeast strains 2011 Ingår i: Seventh International Conference on Renewable Resources and Biorefineries, Belgium. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Fermentation at large industrial scale poses several challenges for the fermenting microorganism to handle. Thus, for an efficient production it is desirable to have robust and efficient strains which can cope with the specific conditions in the process. For bioethanol production by yeast from lignocellulosic material the substrate for growth constitutes one of the largest challenges due to its mixture of sugars and content of inhibitory compounds. Wild-type strains of Saccharomyces cerevisiae can only convert hexose sugars but not the pentoses, xylose and arabinose, which may be present in lignocellulosic material. However, strains have been genetically modified to allow for xylose conversion, but their performance is needed to be improved in terms of rate and efficiency. During the pre-treatment of lignocellulosic material inhibitory compounds are formed; furans, phenolics and organic acids. In an industrial setting, a robust strain back ground (industrial yeast strains) is a prerequisite, in which earlier pentose fermenting traits should be incorporated and further adaptation to the inhibitory compounds need to follow. In the present project, we have used directed evolution to simultaneously improve the inhibitor tolerance and xylose conversion capability of recombinant yeast strains with an industrial background. Improved yeast strains resulting from several strategies were evaluated and one of the best strains with high ethanol production, good xylose utilization capacity, and low xylitol formation was selected for evaluation in larger scale. Fermentations on pre-treated corn cobs were performed with good results regarding ethanol production and xylose utilization both in process development unit scale (15 l) and demonstration scale (10 m3).
29.	Alm, Tove, 1977- (författare) Interaction engineered three-helix bundle domains for protein recovery and detection 2010 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract HTML clipboard The great advances in DNA technology, e.g. sequencing and recombinant DNA techniques, have given us the genetic information and the tools needed to effectively produce recombinant proteins. Recombinant proteins are valuable means in biotechnological applications and are also emerging as alternatives in therapeutic applications. Traditionally, monoclonal antibodies have been the natural choice for biotechnological and therapeutic applications due to their ability to bind a huge range of different molecules and their natural good affinity. However, the large size of antibodies (150 kDa) limits tissue penetration and the recombinant expression is complicated. Therefore, alternative binders with smaller sizes have been derived from antibodies and alternative scaffolds.In this thesis, two structurally similar domains, Zbasic and ABDz1, have been used as purification tags in different contexts. They are both three-helical bundles and derived from bacterial surface domains, but share no sequence homology. Furthermore, by redesign of the scaffold used for ABDz1, a molecule intended for drug targeting with extended in-vivo half-life has been engineered. In Papers I and II, the poly-cationic tag Zbasic is explored and evaluated. Paper I describes the successful investigation of Zbasic as a purification handle under denaturating conditions. Moreover, Zbasic is evaluated as an interaction domain in matrixassisted refolding. Two different proteins were successfully refolded using the same setup without individual optimization. In Paper II, Zbasic is further explored as a purification handle under non-native conditions in a multi-parallel setup. In total, 22 proteins with varying characteristics are successfully purified using a multi-parallel protein purification protocol and a robotic system. Without modifications, the system can purify up to 60 proteins without manual handling. Paper I and II clearly demonstrate that Zbasic can be used as an interaction domain in matrix-assisted refolding and that it offers a good alternative to the commonly used His6-tag under denaturating conditions. In paper III, the small bifunctional ABDz1 is selected from a phage display library. Endowed with two different binding interfaces, ABDz1 is capable of binding both the HSA-sepharose and the protein A-derived MabSelect SuRe-matrix. The bifunctionality of the domain is exploited in an orthogonal affinity setup. Three target proteins are successfully purified using the HSA-matrix and the MabSelect SuRe-matrix. Furthermore, the purity of the target proteins is effectively improved by combining the two chromatographic steps. Thus, paper III shows that the small ABDz1 can be used as an effective purification handle and dual affinity tag without target specific optimization. Paper IV describes the selection and affinity maturation of small bispecific drug-targeting molecules. First generation binders against tumor necrosis factor-α are selected using phage display. Thereafter on-cell surface display and flow cytometry is used to select second-generation binders. The binding to tumor necrosis factor-α is improved up to 30 times as compared to the best first generation binder, and a 6-fold improvement of the binding strength was possible with retained HSA affinity. Paper III and IV clearly demonstrate that dual interaction surfaces can successfully be grafted on a small proteinaceous domain, and that the strategy in paper IV can be used for dual selection of bifunctional binders.
30.	Ask, Magnus, 1983, et al. (författare) Physiological studies of Saccharomyces cerevisiae for increased tolerance against furfural and HMF – two common inhibitors in lignocellulosic hydrolysate 2011 Ingår i: 5th EU-Summer School Proteomic Basics, Brixen, Italy. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract The use of fossil fuels in the transport sector has a significant impact on the environment through the emission of greenhouse gases such as carbon dioxide. Bioethanol is one alternative that has shown potential to at least partly replace fossil fuels. Today’s bioethanol is mainly produced from sugar cane and corn with the yeast Saccharomyces cerevisiae as production organism. Since these raw materials compete with food production, new feedstocks have to be found. A promising alternative is to make use of forest and agricultural residues, so called lignocellulosic materials. Nevertheless, there are many challenges with using lignocellulosic materials for bioethanol production. Since they are recalcitrant to decomposition, harsh conditions have to be used to break down the materials. These conditions tend to produce byproducts that can be inhibitory for the production organism, resulting in lower process productivity. Low productivity is one of the main factors affecting the feasibility of lignocellulosic ethanol production processes. Hydroxymethylfurfural (HMF) and furfural are two compounds that have received a lot of attention during the last years. By studying the effect of these inhibitory compounds on the energy metabolism of S. cerevisiae, the aim of the project is to increase the understanding of the mechanisms by which these inhibitors affect the microorganism. More specifically, the inhibitors effect is studied by quantifying intracellular key compounds such as NADH, NAD+, sugar phosphates and the adenine nucleotide pool. In addition, the biochemical data on intracellular concentrations will be integrated with transcriptomic data. In the future, this knowledge will be used to produce strains that are more tolerant to the process conditions.
31.	Ask, Magnus, 1983, et al. (författare) The effect of pretreatment harshness on separate hydrolysis and fermentation of giant reed by a xylose-consuming Saccharomyces cerevisiae strain 2011 Ingår i: World Congress on Industrial Biotechnology and Bioprocessing, May 8 - 11, 2011, Toronto, Canada. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Bioethanol produced from lignocellulosic feedstocks has received increased attention during the last years. To make lignocellulosic biomass susceptible to enzymatic hydrolysis, the materials first have to be pretreated. The pretreatment is often performed under harsh conditions, which release a number of compounds that can be inhibitory for enzymatic hydrolysis and the subsequent fermentation. Xylooligomers and acetic acid are two compounds that are potential inhibitors of enzymatic hydrolysis and fermentation, respectively. The final concentration of these compounds is highly dependent on the pretreatment conditions. In this study, two different pretreatments with different harshness were performed on giant reed. The influence of the resulting material composition on enzymatic hydrolysis was then investigated. The enzymatic hydrolysis was performed at 10 % (w/w) water insoluble solid concentration (WIS) with Celluclast 1.5L and Novozyme 188 with and without the addition of HTec which is acting on hemicellulose. During the harsher pretreatment, more xylooligomers were produced which were found to have a negative effect on the enzymatic hydrolysis. One of the hydrolysates contained a substantially higher concentration of acetic acid. To investigate the effect of this, the hydrolysed giant reed was fermented with a laboratory Saccharomyces cerevisiae strain, VTT C-10880, carrying the XR/XDH pathway. It was found that the acetic acid had a significant negative effect on the xylose consumption. By supplementing the less harsh pretreated material with the same amount of acetic acid, a similar decrease in xylose consumption was observed, indicating that acetic acid is limiting xylose fermentation in this case.
32.	Bettiga, Maurizio, 1978, et al. (författare) Robust Microorganisms and Process Strategies– The Key to Successful Lignocellulose Based Ethanol Production 2012 Ingår i: ICY 2012 - International Congress on Yeast. Madison, Wisconsin, USA. August 26-30 2012. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Fermentation of lignocellulose raw materials bear a lot of promises, and leave a number of challenges before it can be commercialized with good economical perspectives. The development of the process is driven towards higher gravities and better process integration in order to optimize energy input and water usage. From a microbial point of view this leads to more stressful conditions, including high inhibitor concentrations, high ethanol concentrations and poor nutritional conditions in the hydrolysates to be fermented.One way of addressing these challenges is to optimize the fermentation strategy and here a novel SSF ethanol process configuration involving feeding of substrate, enzyme and yeast will be presented. We demonstrate that this strategy ensures active metabolic state of yeast throughout the process leading to increased ethanol yield and productivity.Another strategy is to improve the microbial robustness by different strain engineering approaches. The inhibitory compounds may influence the cellular metabolism in a number of ways, including direct damage on cellular functions or by perturbations of the cellular energy and redox metabolism. During this presentation the concept of microbial robustness will be discussed and examples of strategies to the design of increased microbial robustness will be given.
33.	Bidgoli, Hossein, et al. (författare) Effect of carboxymethylation conditions on water binding capacity of chitosan-based superabsorbents 2010 Ingår i: Carbohydrate Research. - : Elsevier - Pergamon. - 0008-6215 .- 1873-426X. ; 345:18, s. 2683-2689 Tidskriftsartikel (refereegranskat)abstract A superabsorbent polymer (SAP) from chitosan was provided via carboxymethylation of chitosan, followed by cross-linking with glutaraldehyde and freeze-drying. This work was focused on an investigation of the effects of monochloroacetic acid (MCAA), sodium hydroxide, and reaction time on preparation of carboxymethylchitosan (CMCS). The CMCS products were characterized using FTIR spectroscopy, and their degrees of substitution (DS) were measured using conductimetry and FTIR analysis. The highest DS value was obtained when the carboxymethylation reaction was carried out using 1.75 g MCAA and 1.75 g NaOH per g of chitosan in 4 h. The water solubilities of the CMCS products at various pHs were also evaluated, and the results indicated a significant impact of the reaction parameters on the solubility of CMCS. The CMCSs with the highest DS value resulted in SAPs having the highest water-binding capacity (WBC). TheWBCof the best SAP measured after 10 minexposure in distilled water, 0.9% NaCl solution, synthetic urine, and artificial blood was 104, 33, 30, and 57 g/g, respectively. The WBC of this SAP at pH 2–9 passed a maximum at pH 6.
34.	Chen, Genqiang, et al. (författare) Bioconversion of waste fiber sludge to bacterial nanocellulose and use for reinforcement of CTMP paper sheets 2017 Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:9 Tidskriftsartikel (refereegranskat)abstract Utilization of bacterial nanocellulose (BNC) for large-scale applications is restricted by low productivity in static cultures and by the high cost of the medium. Fiber sludge, a waste stream from pulp and paper mills, was enzymatically hydrolyzed to sugar, which was used for the production of BNC by the submerged cultivation of Komagataeibacter xylinus. Compared with a synthetic glucose-based medium, the productivity of purified BNC from the fiber sludge hydrolysate using shake-flasks was enhanced from 0.11 to 0.17 g/(L × d), although the average viscometric degree of polymerization (DPv) decreased from 6760 to 6050. The cultivation conditions used in stirred-tank reactors (STRs), including the stirring speed, the airflow, and the pH, were also investigated. Using STRs, the BNC productivity in fiber-sludge medium was increased to 0.32 g/(L × d) and the DPv was increased to 6650. BNC produced from the fiber sludge hydrolysate was used as an additive in papermaking based on the chemithermomechanical pulp (CTMP) of birch. The introduction of BNC resulted in a significant enhancement of the mechanical strength of the paper sheets. With 10% (w/w) BNC in the CTMP/BNC mixture, the tear resistance was enhanced by 140%. SEM images showed that the BNC cross-linked and covered the surface of the CTMP fibers, resulting in enhanced mechanical strength.
35.	Enoksson, Peter, 1957, et al. (författare) Micro- and Nanosystems for Sensing in Medicine 2008 Ingår i: Proceedings of Medicinteknikdagarna 2008, 14-15 October, Göteborg, Sweden. ; , s. 117- Konferensbidrag (övrigt vetenskapligt/konstnärligt)
36.	Ferreira, Jorge A., et al. (författare) Spent sulphite liquor for cultivation of an edible Rhizopus sp. 2012 Ingår i: BioResources. - : North Carolina State University: College of Natural Resources. - 1930-2126. ; 7:1, s. 173-188 Tidskriftsartikel (refereegranskat)abstract Spent sulphite liquor, the major byproduct from the sulphite pulp production process, was diluted to 50% and used for production of an edible zygomycete Rhizopus sp. The focus was on production, yield, and composition of the fungal biomass composition. The fungus grew well at 20 to 40°C, but 32°C was found to be preferable compared to 20 and 40°C in terms of biomass production and yield (maximum of 0.16 g/g sugars), protein content (0.50-0.60 g/g), alkali-insoluble material (AIM) (ca 0.15 g/g), and glucosamine content (up to 0.30 g/g of AIM). During cultivation in a pilot airlift bioreactor, the yield increased as aeration was raised from 0.15 to 1.0 vvm, indicating a high demand for oxygen. After cultivation at 1.0 vvm for 84 h, high yield and production of biomass (up to 0.34 g/g sugars), protein (0.30-0.50 g/g), lipids (0.02-0.07 g/g), AIM (0.16-0.28 g/g), and glucosamine (0.22-0.32 g/g AIM) were obtained. The fungal biomass produced from spent sulphite liquor is presently being tested as a replacement for fishmeal in feed for fish aquaculture and seems to be a potential source of nutrients and for production of glucosamine.
37.	Hjortmo, Sofia, 1978 (författare) On Folates in Yeasts -Exploring Yeasts as Vehicles for Biofortification of Folates in Food 2008 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract High intake of the B vitamin folate during pregnancy is known to decrease the risk for development of neural tube defects. In addition, a good folate status may prevent the progression of several diseases such as megaloblastic anaemia, cardiovascular disease, cancer and Alzheimer’s disease. However, reaching sufficient amounts via the diet only is complicated and new strategies must be developed to increase the mean folate intake. The aim of this thesis is to explore the use of yeasts for biofortification of folates in food. Yeasts synthesise folates de novo and may constitute potent vehicles for natural folates. Current work includes investigations of folate content and composition in yeasts as well as studies of the impact of growth rate and chemical environments on folate levels in Saccharomyces cerevisiae (Baker’s yeast). The applicability of the results was then investigated in two food model systems (bread and a cereal-based fermented porridge called togwa) to demonstrate the practical relevance. In a screening of 52 yeast strains, the folate content ranged from 40 to 145 µg per gram dry matter of yeast, showing that inherent variations in yeast folate levels exist. Several S. cerevisiae strains showed at least a two-fold higher folate content than a commercial Baker’s strain, indicating possibilities to increase folates in fermented foods simply by choosing the proper strain. With regard to cultivation conditions, folates in S. cerevisiae were demonstrated to increase linearly with growth rate in a defined medium, showing that high growth rate, i.e. respiro-fermentative metabolism, is most favourable for high folate content. Cultivation in a rich medium yielded cells containing lower amounts of folate compared to cells grown in a poor chemical environment even though the specific growth rate was higher in the rich medium. The results obtained show that the growth rate per se could not predict intracellular folate concentrations and that the chemical environment has a substantial impact on intracellular folates. By applying strain selection and cultivation at optimal conditions prior to baking we were able to increase folates five-fold in white wheat bread compared to bread leavened with commercial Baker’s yeast. In addition, folates increased at most 23-fold during yeast fermentations in a cereal-based porridge (togwa) compared to togwa raw material. Final folate levels were shown to be highly dependent on strain and cultivation time. The results demonstrate that yeasts constitute flexible and controllable vehicles for biofortification of folates in fermented food.
38.	Juul, Louise, et al. (författare) Ulva fenestrata protein – comparison of three extraction methods with respect to protein yield and protein quality 2021 Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 60 Tidskriftsartikel (refereegranskat)abstract Seaweed is gaining attention as a possible alternative and sustainable source of proteins. This study investigates three protein extraction methods and their effect on protein yield and quality when applied to Ulva fenestrata . Two of the methods included alkaline extractions (pH-shifts); one version solubilizing the proteins at pH 8.5 and one solubilizing them at pH 8.5 followed by pH 12 (pH 8.5+12). The third method was a mechanical pressing, using a double screw press. All extraction methods were followed by isoelectric precipitation to concentrate the proteins. Extraction at pH 8.5 gave the significantly highest total protein yield after the isoelectric precipitation, followed by extraction at pH 8.5+12 and lastly mechanical extraction gave the lowest yield. Proteins extracted with both alkaline methods had a significantly higher solubility at pH 7 and pH 9, compared to proteins from the mechanical pressing. There were no significant differences between the three methods in total D/L-amino acid ratio. Amino acid cross-links measured as lysinoalanine (LAL) and lanthionine (LAN) where found in significantly higher amounts in alkali-extracted proteins compared to mechanically extracted, however not to a degree that expect to compromise functional or nutritional quality. Further, no significant difference in protein in vitro digestibility was found between extraction methods. In conclusion, results indicated that protein extraction at pH 8.5 can be recommended, especially regarding total protein yield and solubility of the final protein extract.
39.	Karimi, Keikhosro, et al. (författare) Mucor indicus as a biofilter and fermenting organism in continuous ethanol production from lignocellulosic hydrolyzate 2008 Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X .- 1873-295X. ; 39:2, s. 383-388 Tidskriftsartikel (refereegranskat)
40.	Kurniawan, Tonny, et al. (författare) Semi-continuous reverse membrane bioreactor in two-stage anaerobic digestion of citruswaste 2018 Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 11:8 Tidskriftsartikel (refereegranskat)abstract The presence of an antimicrobial compound called D-Limonene in citrus waste inhibits methane production from such waste in anaerobic digestion. In this work, a two-stage anaerobic digestion method is developed using reverse membrane bioreactors (rMBRs) containing cells encased in hydrophilic membranes. The purpose of encasement is to retain a high cell concentration inside the bioreactor. The effectiveness of rMBRs in reducing cell washout is evaluated. Three different system configurations, comprising rMBRs, freely suspended cells (FCs), and a combination of both (abbreviated to rMBR-FCs), are incubated at three different organic loading rates (OLRs) each, namely 0.6, 1.2, and 3.6 g COD/(L cycle). Incubation lasts for eight feeding cycles at 55 °C. Methane yield and biogas composition results show that rMBRs perform better than rMBR-FCs and FCs at all three OLRs. Volatile fatty acid profiles and H2production show that the reactors are working properly and no upset occurs. Additionally, a short digestion time of 4 days can be achieved using the rMBR configuration in this study.
41.	Lennartsson, Patrik R, 1983, et al. (författare) Effects of different growth forms of Mucor indicus on cultivation on dilute-acid lignocellulosic hydrolyzate, inhibitor tolerance, and cell wall composition 2009 Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 143:4, s. 255-261 Tidskriftsartikel (refereegranskat)abstract The dimorphic fungus Mucor indicus was grown in different forms classified as purely filamentous, mostly filamentous, mostly yeast-like and purely yeast-like, and the relationship between morphology and metabolite production, inhibitor tolerance and the cell wall composition was investigated. Low concentrations of spores in the inoculum with subsequent aeration promoted filamentous growth, whereas higher spore concentrations and anaerobic conditions promoted yeast-like growth. Ethanol was the main metabolite with glycerol next under all conditions tested. The yields of ethanol from glucose were between 0.39 and 0.42 g g(-1) with productivities of 3.2-5.0 g l(-1) h(-1). The ethanol productivity of mostly filamentous cells was increased from 3.9 to 5.0 g l(-1) h(-1) by the presence of oxygen, whereas aeration of purely yeast-like cells showed no such effect. All growth forms were able to tolerate 4.6 g l(-1) furfural and 10 g l(-1) acetic acid and assimilate the sugars, although with different consumption rates. The cell wall content of the fungus measured as alkali insoluble materials (AIM) of the purely yeast-like cells was 26% of the biomass, compared to 8% of the pure filaments. However, the chitosan concentration of the filaments was 29% of the AIM, compared to 6% of the yeast-like cells.
42.	Millati, Ria, 1972, et al. (författare) Anaerobic digestion of citrus waste using two-stage membrane bioreactor 2018 Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 316:1 Konferensbidrag (refereegranskat)abstract Anaerobic digestion is a promising method to treat citrus waste. However, the presence of limonene in citrus waste inhibits anaerobic digestion process. Limonene is an antimicrobial compound and could inhibit methane forming bacteria that takes a longer time to recover than the injured acid forming bacteria. Hence, volatile fatty acids will be accumulated and methane production will be decreased. One way to solve this problem is by conducting anaerobic digestion process into two stages. The first step is aimed for hydrolysis, acidogenesis, and acetogenesis reactions and the second stage is aimed for methanogenesis reaction. The separation of the system would further allow each stage in their optimum conditions making the process more stable. In this research, anaerobic digestion was carried out in batch operations using 120 ml-glass bottle bioreactors in 2 stages. The first stage was performed in free-cells bioreactor, whereas the second stage was performed in both bioreactor of free cells and membrane bioreactor. In the first stage, the reactor was set into 'anaerobic' and 'semi-aerobic' conditions to examine the effect of oxygen on facultative anaerobic bacteria in acid production. In the second stage, the protection of membrane towards the cells against limonene was tested. For the first stage, the basal medium was prepared with 1.5 g VS of inoculum and 4.5 g VS of citrus waste. The digestion process was carried out at 55°C for four days. For the second stage, the membrane bioreactor was prepared with 3 g of cells that were encased and sealed in a 3×6 cm 2 polyvinylidene fluoride membrane. The medium contained 40 ml basal medium and 10 ml liquid from the first stage. The bioreactors were incubated at 55°C for 2 days under anaerobic condition. The results from the first stage showed that the maximum total sugar under 'anaerobic' and 'semi-aerobic' conditions was 294.3 g/l and 244.7 g/l, respectively. The corresponding values for total volatile fatty acids were 3.8 g/l and 2.9 g/l, respectively. Methane production of citrus waste taken from the first stage under 'anaerobic' condition in membrane and free-cells bioreactors was 11.2 Nml and 7.2 Nml, respectively. Whereas, methane production of citrus waste taken from the first stage under 'semi-aerobic' condition in membrane and free-cells bioreactors was 8.8 Nml and 5.7 Nml, respectively. It can be seen from the results of the first stage that volatile fatty acids from 'anaerobic' condition was higher than that of 'semi-aerobic' condition. The absence of oxygen provides the optimal condition for growth and metabolism of facultative and obligatorily anaerobic bacteria in the first stage. Furthermore, polyvinylidene fluoride membrane was able to protect the cells from antimicrobial compounds.
43.	Millati, Ria, 1972, et al. (författare) Ethanol from Oil Palm Empty Fruit Bunch via Dilute-Acid Hydrolysis and Fermentation by Mucor indicus and Saccharomyces cerevisiae 2011 Ingår i: Agricultural Journal. - : Medwell Journals. - 1994-4616 .- 1816-9155. ; 6:2, s. 54-59 Tidskriftsartikel (refereegranskat)abstract Oil Palm Empty Fruit Bunch (OPEFB) was hydrolyzed in a one-stage hydrolysis using dilute-sulfuric acid (0.2, 0.8%) at 170-230°C with a holding time of 5 and 15 min. The maximum yield of xylose was 135.94 g kg-1 OPEFB, obtained at 0.8% acid, 190°C and 5 min. The maximum yield of glucose was 62.70 g kg-1 OPEFB, obtained at 0.8% acid, 210°C and 5 min. Based on these results, two-stage hydrolysis was performed to produce hydrolyzates for the fermentation process. Hydrolyzate from the first stage was fermented by Mucor indicus while the hydrolyzate from the second stage was fermented by Saccharomyces cerevisiae. The corresponding ethanol yields were 0.45 and 0.46 g ethanol g-1 sugar consumed.
44.	Millati, Ria, 1972, et al. (författare) Ethanol production from xylose and wood hydrolyzate by Mucor indicus at different aeration rates 2008 Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 3:4, s. 1020-1029 Tidskriftsartikel (refereegranskat)abstract The fungus Mucor indicus is able to produce ethanol from xylose as well as dilute-acid lignocellulosic hydrolyzates. The fungus completely assimilated 10 g/L xylose as the sole carbon and energy source within 32 to 65 h at an aeration rate of 0.1 to 1.0 vvm. The highest ethanol yield was 0.16 g/g at 0.1 vvm. Xylitol was formed intermediately with a maximum yield of 0.22 g/g at 0.5 vvm., but disappeared towards the end of experiments. During cultivation in a mixture of xylose and glucose, the fungus did not assimilate xylose as long as glucose was present in the medium. The anaerobic cultivation of the fungus in the hydrolyzate containing 20% xylose and 80% hexoses resulted in no assimilation of xylose but complete consumption of the hexoses in less than 15 h. The ethanol yield was 0.44 g/g. However, the xylose in the hydrolyzate was consumed when the media were aerated at 0.067 to 0.333 vvm. The best ethanol yield was 0.44 g/g at 0.067 vvm. The results of this study suggest that M. indicus hydrolyzate can be first fermented anaerobically for hexose assimilation and subsequently continued under oxygen-limited conditions for xylose fermentation.
45.	Munthe, Christian, 1962 (författare) From synthetic genome to synthetic life: prospects as well as perils of gene technology exponentially multiplied : Från syntetiska gener till syntetiskt liv: såväl framtidsutsikter som risker med gentekniken exponentiellt mångfaldigade 2010 Ingår i: Philosophical Comment Blog. ; :2010-05-20 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
46.	Munthe, Christian, 1962 (författare) Grow Your Steak? The Case for In Vitro Meat 2010 Ingår i: Philosophical Comment Blog. ; :2010-09-01 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
47.	Munthe, Christian, 1962 (författare) Will the Synthetic Genome Breakthrough Be Any Good? - Reasons for Doubt 2010 Ingår i: Philosophical Comment Blog. Annan publikation (övrigt vetenskapligt/konstnärligt)
48.	Olsson, Joakim, 1988, et al. (författare) Ensiling of Saccharina latissima and Laminaria digitata with organic acid additives 2016 Ingår i: Nordic Seaweed Conference, 12-13 October, Grenå. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Seaweeds are a promising source of biomass to provide food, fuels and chemicals in a sustainable future. However, some issues for a biorefinery are that its composition as well as availability varies seasonally and a fresh source cannot be provided all year around. To secure a steady biomass supply the harvest has to be preserved and today drying (especially sun-drying) is commonly used for seaweeds in the carrageenan industry. In colder climates, however, relying on sun-drying could be more problematic and energy intensive drying utilizing hot air is the alternative.An alternative method is ensiling, which is common in agriculture for preserving animal feed. Ensiling is not well researched for seaweeds, though it is receiving more and more attention. It offers a low energy alternative for preservation that relies on acidification by lactic acid bacteria in an anaerobic environment efficiently hampering growth of unwanted microbes. To ensure that the microbial community is beneficial for a good ensiling process additives can be used e.g. inoculum, organic acids, enzymes and sugars. In this study, six different organic acids have been tested at three different concentrations to investigate them as potential additives for ensiling of Saccharina latissima and Laminaria digitata. The content of protein and the monosaccharide profile in the biomass has been analysed before and after 90 days of ensiling to elucidate how the preservation process affects the biomass composition. Such knowledge is important for a biorefinery of seaweeds.
49.	Pour Bafrani, Mohammad, 1981, et al. (författare) Protective Effect of Encapsulation in Fermentation of Limonene-contained Media and Orange Peel Hydrolyzate 2007 Ingår i: International Journal of Molecular Science. ; 8:8, s. 777-787 Tidskriftsartikel (refereegranskat)
50.	Sárvári Horváth, Ilona, 1960, et al. (författare) Effects of furfural on the respiratory metabolism of Saccharomyces cerevisiae in glucose-limited chemostats 2003 Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 69:7, s. 4076-4086 Tidskriftsartikel (refereegranskat)abstract Effects of furfural on the aerobic metabolism of the yeast Saccharomyces cerevisiae were studied by performing chemostat experiments, and the kinetics of furfural conversion was analyzed by performing dynamic experiments. Furfural, an important inhibitor present in lignocellulosic hydrolysates, was shown to have an inhibitory effect on yeast cells growing respiratively which was much greater than the inhibitory effect previously observed for anaerobically growing yeast cells. The residual furfural concentration in the bioreactor was close to zero at all steady states obtained, and it was found that furfural was exclusively converted to furoic acid during respiratory growth. A metabolic flux analysis showed that furfural affected fluxes involved in energy metabolism. There was a 50% increase in the specific respiratory activity at the highest steady-state furfural conversion rate. Higher furfural conversion rates, obtained during pulse additions of furfural, resulted in respirofermentative metabolism, a decrease in the biomass yield, and formation of furfuryl alcohol in addition to furoic acid. Under anaerobic conditions, reduction of furfural partially replaced glycerol formation as a way to regenerate NAD+. At concentrations above the inlet concentration of furfural, which resulted in complete replacement of glycerol formation by furfuryl alcohol production, washout occurred. Similarly, when the maximum rate of oxidative conversion of furfural to furoic acid was exceeded aerobically, washout occurred. Thus, during both aerobic growth and anaerobic growth, the ability to tolerate furfural appears to be directly coupled to the ability to convert furfural to less inhibitory compounds.

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