| 1. |
- Mayers, Joshua, 1988, et al.
(författare)
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Integrating Microalgal Production with Industrial Outputs - Reducing Process Inputs and Quantifying the Benefits
- 2016
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Ingår i: Industrial Biotechnology. - : Mary Ann Liebert Inc. - 1550-9087 .- 1931-8421. ; 12:4, s. 219-234
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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.
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| 2. |
- Wang, Ruifei, 1985, et al.
(författare)
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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
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 9:1, s. 88-
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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.
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| 3. |
- Ylitervo, Päivi, et al.
(författare)
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Continuous Ethanol Production with a Membrane Bioreactor at High Acetic Acid Concentrations
- 2014
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Ingår i: Membranes. - : MDPI. - 2077-0375. ; 4:3, s. 372-387
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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.
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| 4. |
- Jansson, Ronnie, et al.
(författare)
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Functionalized silk assembled from a recombinant spider silk fusion protein (Z-4RepCT) produced in the methylotrophic yeast Pichia pastoris
- 2016
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Ingår i: Biotechnology Journal. - : Wiley-VCH Verlagsgesellschaft. - 1860-6768 .- 1860-7314. ; 11:5, s. 687-699
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Tidskriftsartikel (refereegranskat)abstract
- Functional biological materials are a growing research area with potential applicability in medicine and biotechnology. Using genetic engineering, the possibility to introduce additional functions into spider silk-based materials has been realized. Recently, a recombinant spider silk fusion protein, Z-4RepCT, was produced intracellularly in Escherichia coli and could after purification self-assemble into silk-like fibers with ability to bind antibodies via the IgG-binding Z domain. In this study, the use of the methylotrophic yeast Pichia pastoris for production of Z-4RepCT has been investigated. Temperature, pH and production time were influencing the amount of soluble Z-4RepCT retrieved from the extracellular fraction. Purification of secreted Z-4RepCT resulted in a mixture of full-length and degraded silk proteins that failed to self-assemble into fibers. A position in the C-terminal domain of 4RepCT was identified as being subjected to proteolytic cleavage by proteases in the Pichia culture supernatant. Moreover, the C-terminal domain was subjected to glycosylation during production in P. pastoris. These observed alterations of the CT domain are suggested to contribute to the failure in fiber assembly. As alternative approach, Z-4RepCT retrieved from the intracellular fraction, which was less degraded, was used and shown to retain ability to assemble into silk-like fibers after enzymatic deglycosylation.
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| 5. |
- McKee, Lauren S., et al.
(författare)
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A GH115 alpha-glucuronidase from Schizophyllum commune contributes to the synergistic enzymatic deconstruction of softwood glucuronoarabinoxylan
- 2016
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Ingår i: Biotechnology for Biofuels. - : BioMed Central. - 1754-6834. ; 9
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Tidskriftsartikel (refereegranskat)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.
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| 6. |
- Skoog, Emma, 1983, et al.
(författare)
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Biobased adipic acid – The challenge of developing the production host
- 2018
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 36:8, s. 2248-2263
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Forskningsöversikt (refereegranskat)abstract
- Adipic acid is a platform chemical, and is the most important commercial dicarboxylic acid. It has been targeted for biochemical conversion as an alternative to present chemical production routes. From the perspective of bioeconomy, several kinds of raw material are of interest including the sugar platform (derived from starch, cellulose or hemicellulose), the lignin platform (aromatics) and the fatty acid platform (lipid derived). Two main biochemical-based production schemes may be employed: (i) direct fermentation to adipic acid, or (ii) fermentation to muconic or glucaric acid, followed by chemical hydrogenation (indirect fermentation). This review presents a comprehensive description of the metabolic pathways that could be constructed and analyzes their respective theoretical yields and metabolic constraints. The experimental yields and titers obtained so far are low, with the exception of processes based on palm oil and glycerol, which have been reported to yield up to 50 g and 68 g adipic acid/L, respectively. The challenges that remain to be addressed in order to achieve industrially relevant production levels include solving redox constraints, and identifying and/or engineering enzymes for parts of the metabolic pathways that have yet to be metabolically demonstrated. This review provides new insights into ways in which metabolic pathways can be constructed to achieve efficient adipic acid production. The production host provides the chassis to be engineered via an appropriate metabolic pathway, and should also have properties suitable for the industrial production of adipic acid. An acidic process pH is attractive to reduce the cost of downstream processing. The production host should exhibit high tolerance to complex raw material streams and high adipic acid concentrations at acidic pH.
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| 7. |
- Svensson, Sofie, et al.
(författare)
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Fungal textiles : Wet spinning of fungal microfibers to produce monofilament yarns
- 2021
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Ingår i: Sustainable Materials and Technologies. - : Elsevier BV. - 2214-9937. ; 28
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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.
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| 8. |
- Westman, Johan, 1983, et al.
(författare)
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Current progress in high cell density yeast bioprocesses for bioethanol production
- 2015
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Ingår i: Biotechnology journal. - : Wiley. - 1860-6768 .- 1860-7314. ; 10:8, s. 1185-1195
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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.
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| 9. |
- Gontia, Paul, 1984, et al.
(författare)
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Life cycle assessment of bio-based sodium polyacrylate production from pulp mill side streams: Case study of thermo-mechanical and sulfite pulp mills
- 2016
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 131, s. 475-484
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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.
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| 10. |
- Karlsson, Emma, 1983, et al.
(författare)
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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
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 13:2
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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.
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