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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)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.
  • Gullfot, Fredrika, 1967- (författare)
  • Synthesis of xyloglucan oligo- and polysaccharides with glycosynthase technology
  • 2009
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • <p>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.</p> <p>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.</p> <p>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.</p>
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3.
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4.
  • 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)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?
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5.
  • 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)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.
6.
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7.
  • 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)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.
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8.
  • Mayers, Joshua, 1988-, et al. (författare)
  • Integrating Microalgal Production with Industrial Outputs - Reducing Process Inputs and Quantifying the Benefits
  • 2016
  • Ingår i: Alger till biobaserade kemikalier - Förutsättningar för industriell odling av mikroalger i Nordeuropa.
  • 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.
9.
  • 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. - 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.
10.
  • Ylitervo, Päivi, 1983- (författare)
  • Concepts for improving ethanol productivity from lignocellulosic materials: Encapsulated yeast and membrane bioreactors
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt)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.
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