| 1. |
- Munthe, Christian, 1962
(author)
-
Precaution and Ethics: Handling risks, uncertainties and knowledge gaps in the regulation of new biotechnologies
- 2017
-
Book (other academic/artistic)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
(author)
-
Towards More Robust Saccharomyces cerevisiae Strains for Lignocellulosic Bioethanol Production: Lessons from process concepts and physiological investigations
- 2013
-
Doctoral thesis (other academic/artistic)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.
(author)
-
Multifeed simultaneous saccharification and fermentation enables high gravity submerged fermentation of lignocellulose.
- 2015
-
In: Recent Advances in Fermentation Technology (RAFT 11), Clearwater Beach, Florida, USA, November 8-11, 2015. Oral presentation..
-
Conference paper (other academic/artistic)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.
(author)
-
Integrating Microalgal Production with Industrial Outputs - Reducing Process Inputs and Quantifying the Benefits
- 2016
-
In: Industrial Biotechnology. - : Mary Ann Liebert Inc. - 1550-9087 .- 1931-8421. ; 12:4, s. 219-234
-
Journal article (peer-reviewed)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.
(author)
-
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
-
In: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 9:1, s. 88-
-
Journal article (peer-reviewed)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
(author)
-
Concepts for improving ethanol productivity from lignocellulosic materials : encapsulated yeast and membrane bioreactors
- 2014
-
Doctoral thesis (other academic/artistic)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.
(author)
-
Continuous Ethanol Production with a Membrane Bioreactor at High Acetic Acid Concentrations
- 2014
-
In: Membranes. - : MDPI. - 2077-0375. ; 4:3, s. 372-387
-
Journal article (peer-reviewed)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. |
- Anasontzis, George E, 1980
(author)
-
Biomass modifying enzymes: From discovery to application
- 2012
-
In: Oral presentation at the Chalmers Life Science AoA conference.
-
Conference paper (other academic/artistic)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?
|
|
| 9. |
|
|
| 10. |
- McKee, Lauren S., et al.
(author)
-
A GH115 alpha-glucuronidase from Schizophyllum commune contributes to the synergistic enzymatic deconstruction of softwood glucuronoarabinoxylan
- 2016
-
In: Biotechnology for Biofuels. - : BioMed Central. - 1754-6834. ; 9
-
Journal article (peer-reviewed)abstract
- Background: Lignocellulosic biomass from softwood represents a valuable resource for the production of biofuels and bio-based materials as alternatives to traditional pulp and paper products. Hemicelluloses constitute an extremely heterogeneous fraction of the plant cell wall, as their molecular structures involve multiple monosaccharide components, glycosidic linkages, and decoration patterns. The complete enzymatic hydrolysis of wood hemicelluloses into monosaccharides is therefore a complex biochemical process that requires the activities of multiple degradative enzymes with complementary activities tailored to the structural features of a particular substrate. Glucuronoarabinoxylan (GAX) is a major hemicellulose component in softwood, and its structural complexity requires more enzyme specificities to achieve complete hydrolysis compared to glucuronoxylans from hardwood and arabinoxylans from grasses. Results: We report the characterisation of a recombinant alpha-glucuronidase (Agu115) from Schizophyllum commune capable of removing (4-O-methyl)-glucuronic acid ((Me) GlcA) residues from polymeric and oligomeric xylan. The enzyme is required for the complete deconstruction of spruce glucuronoarabinoxylan (GAX) and acts synergistically with other xylan-degrading enzymes, specifically a xylanase (Xyn10C), an alpha-l-arabinofuranosidase (AbfA), and a beta-xylosidase (XynB). Each enzyme in this mixture showed varying degrees of potentiation by the other activities, likely due to increased physical access to their respective target monosaccharides. The exo-acting Agu115 and AbfA were unable to remove all of their respective target side chain decorations from GAX, but their specific activity was significantly boosted by the addition of the endo-Xyn10C xylanase. We demonstrate that the proposed enzymatic cocktail (Agu115 with AbfA, Xyn10C and XynB) achieved almost complete conversion of GAX to arabinofuranose (Araf), xylopyranose (Xylp), and MeGlcA monosaccharides. Addition of Agu115 to the enzymatic cocktail contributes specifically to 25 % of the conversion. However, traces of residual oligosaccharides resistant to this combination of enzymes were still present after deconstruction, due to steric hindrances to enzyme access to the substrate. Conclusions: Our GH115 alpha-glucuronidase is capable of finely tailoring the molecular structure of softwood GAX, and contributes to the almost complete saccharification of GAX in synergy with other exo- and endo-xylan-acting enzymes. This has great relevance for the cost-efficient production of biofuels from softwood lignocellulose.
|
|
| 11. |
|
|
| 12. |
- Shin, Jae Ho, 1987, et al.
(author)
-
Molecular docking and linear interaction energy studies give insight to α, β-reduction of enoate groups in enzymes
- 2018
-
Conference paper (other academic/artistic)abstract
- Production of adipic acid from renewable sources has been gaining attention in an attempt to move from an oil-based economy to a biobased economy. Metabolic engineering allows microorganisms to produce useful chemicals using renewable resources as carbon sources. We target a theoretical metabolic pathway that relies on conversion of L-lysine to adipic acid. One of the enzymatic steps in this conversion pathway is an α, β-reduction of an unsaturated bond in an enoate moiety and no aerobic enzymes have been identified to specifically make this conversion on 6-amino-trans-2-hexenoic acid. We evaluated Escherichia coli NemA, and Saccharomyces pastorianus Oye1 (Old Yellow Enzyme 1) for their potenstial capability to carry out the desired α, β-reduction. Here, we build homology models for E. coli NemA and perform molecular docking studies of trans-2-hexenoic acid and trans-2-hexenal to the candidate enzyme models. Ligand-enzyme binding stability is assessed by molecular dynamics (MD) simulations. Additionally, linear energy calculations were used to investigate binding stability in solution environment. Here, we propose that NemA and Oye1, both belonging to the Old yellow enzyme family, have large enough catalytic pocket for accommodating enoate moieties but not enough stability to carry out the α, β-reduction. Protein engineering of both NemA and Oye1 would be necessary for these enzymes to perform the targeted reactions efficiently. The results shown in this study provides a useful insight to α, β-reduction reaction potentially crucial in bio-based production of adipic acid.
|
|
| 13. |
- Skoog, Emma, 1983, et al.
(author)
-
Biobased adipic acid – The challenge of developing the production host
- 2018
-
In: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 36:8, s. 2248-2263
-
Research review (peer-reviewed)abstract
- Adipic acid is a platform chemical, and is the most important commercial dicarboxylic acid. It has been targeted for biochemical conversion as an alternative to present chemical production routes. From the perspective of bioeconomy, several kinds of raw material are of interest including the sugar platform (derived from starch, cellulose or hemicellulose), the lignin platform (aromatics) and the fatty acid platform (lipid derived). Two main biochemical-based production schemes may be employed: (i) direct fermentation to adipic acid, or (ii) fermentation to muconic or glucaric acid, followed by chemical hydrogenation (indirect fermentation). This review presents a comprehensive description of the metabolic pathways that could be constructed and analyzes their respective theoretical yields and metabolic constraints. The experimental yields and titers obtained so far are low, with the exception of processes based on palm oil and glycerol, which have been reported to yield up to 50 g and 68 g adipic acid/L, respectively. The challenges that remain to be addressed in order to achieve industrially relevant production levels include solving redox constraints, and identifying and/or engineering enzymes for parts of the metabolic pathways that have yet to be metabolically demonstrated. This review provides new insights into ways in which metabolic pathways can be constructed to achieve efficient adipic acid production. The production host provides the chassis to be engineered via an appropriate metabolic pathway, and should also have properties suitable for the industrial production of adipic acid. An acidic process pH is attractive to reduce the cost of downstream processing. The production host should exhibit high tolerance to complex raw material streams and high adipic acid concentrations at acidic pH.
|
|
| 14. |
- Bettiga, Maurizio, 1978, et al.
(author)
-
Robust S. cerevisiae strain for next generation bio-processes: concepts and case-studies
- 2013
-
In: Cell Factories and Biosustainability (Hilleroed, Denmark, May 5-8 2013).
-
Conference paper (other academic/artistic)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.
|
|
| 15. |
- Bettiga, Maurizio, 1978, et al.
(author)
-
Robust S. cerevisiae strain for next generation bio-processes: concepts and case-studies
- 2013
-
In: 35th Symposium on Biotechnology for Fuels and Chemicals (Portland, OR. April 29-May 2, 2013).
-
Conference paper (other academic/artistic)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.
|
|
| 16. |
|
|
| 17. |
- Westman, Johan
(author)
-
Ethanol production from lignocellulose using high local cell density yeast cultures. Investigations of flocculating and encapsulated Saccharomyces cerevisiae
- 2014
-
Doctoral thesis (other academic/artistic)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.
|
|
| 18. |
- Jansson, Ronnie, et al.
(author)
-
Functionalized silk assembled from a recombinant spider silk fusion protein (Z-4RepCT) produced in the methylotrophic yeast Pichia pastoris
- 2016
-
In: Biotechnology Journal. - : Wiley-VCH Verlagsgesellschaft. - 1860-6768 .- 1860-7314. ; 11:5, s. 687-699
-
Journal article (peer-reviewed)abstract
- Functional biological materials are a growing research area with potential applicability in medicine and biotechnology. Using genetic engineering, the possibility to introduce additional functions into spider silk-based materials has been realized. Recently, a recombinant spider silk fusion protein, Z-4RepCT, was produced intracellularly in Escherichia coli and could after purification self-assemble into silk-like fibers with ability to bind antibodies via the IgG-binding Z domain. In this study, the use of the methylotrophic yeast Pichia pastoris for production of Z-4RepCT has been investigated. Temperature, pH and production time were influencing the amount of soluble Z-4RepCT retrieved from the extracellular fraction. Purification of secreted Z-4RepCT resulted in a mixture of full-length and degraded silk proteins that failed to self-assemble into fibers. A position in the C-terminal domain of 4RepCT was identified as being subjected to proteolytic cleavage by proteases in the Pichia culture supernatant. Moreover, the C-terminal domain was subjected to glycosylation during production in P. pastoris. These observed alterations of the CT domain are suggested to contribute to the failure in fiber assembly. As alternative approach, Z-4RepCT retrieved from the intracellular fraction, which was less degraded, was used and shown to retain ability to assemble into silk-like fibers after enzymatic deglycosylation.
|
|
| 19. |
- Olsson, Lisbeth, 1963, et al.
(author)
-
Microbial robustness in bioprocesses
- 2023
-
Conference paper (other academic/artistic)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.
|
|
| 20. |
- Svensson, Sofie, et al.
(author)
-
Fungal textiles : Wet spinning of fungal microfibers to produce monofilament yarns
- 2021
-
In: Sustainable Materials and Technologies. - : Elsevier BV. - 2214-9937. ; 28
-
Journal article (peer-reviewed)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.
|
|
| 21. |
- Westman, Johan, 1983, et al.
(author)
-
Current progress in high cell density yeast bioprocesses for bioethanol production
- 2015
-
In: Biotechnology journal. - : Wiley. - 1860-6768 .- 1860-7314. ; 10:8, s. 1185-1195
-
Research review (peer-reviewed)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.
|
|
| 22. |
- Gullfot, Fredrika, 1967-
(author)
-
Synthesis of xyloglucan oligo- and polysaccharides with glycosynthase technology
- 2009
-
Licentiate thesis (other academic/artistic)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.
|
|
| 23. |
- Hong, Kuk-ki, 1976, et al.
(author)
-
Metabolic Engineering of Saccharomyces cerevisiae: A Key Cell Factory Platform for Future Biorefineries
- 2012
-
In: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-9071 .- 1420-682X. ; 69:16, s. 2671-2690
-
Research review (peer-reviewed)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.
|
|
| 24. |
- Sunner, Hampus, 1981, et al.
(author)
-
Fungal Ferulic Acid Esterases – Specificity and Phylogeny
- 2009
-
In: Italic5 Science and Technology of Biomasses Proceedings Book, M Orlandi, C Crestine (Ed.). Italic5/COST conference, Sept 1-4 2009, Varenna, Italy.
-
Conference paper (other academic/artistic)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.
|
|
| 25. |
- Gontia, Paul, 1984, et al.
(author)
-
Life cycle assessment of bio-based sodium polyacrylate production from pulp mill side streams: Case study of thermo-mechanical and sulfite pulp mills
- 2016
-
In: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 131, s. 475-484
-
Journal article (peer-reviewed)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.
|
|
