| 1. |
- Janssen, Mathias, 1973, et al.
(författare)
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Life cycle assessment of wood-based ethanol production at high gravity conditions
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The development of economically feasible and environmentally benign processes for the production of second generation biofuels is an ongoing effort. The production of bio-ethanol from wood (spruce) using high gravity (high solids content) fermentation is one process concept that is currently under development. Such a process will lead to lower water use in the process, and consequently to lower energy use. However, high gravity conditions have adverse effects on the micro-organisms and high yields are thus not guaranteed. All this will affect the environmental impact of the process. Life cycle assessment (LCA) is used to evaluate the environmental impact of the process along its development path. The main objective of the LCA is to help improve the process under development from an environmental point of view. The LCA is based on the results of lab experiments that were done for the high gravity fermentation process using pretreated spruce as the feedstock. These experiments focused on the process configuration and detoxification strategies in order to increase yields. A spreadsheet model was set up that used the experimental data in order to calculate the mass and energy balances of the system under study, from the harvesting of the wood until the produced ethanol leaves the plant (cradle-to-gate). The results of the mass and energy balances were subsequently used in the LCA model in order to calculate the environmental impact of the ethanol production. The outcomes of the LCA for all the process variants studied were compared in order to identify the weak and strong points of the process. This information can then be used for further development of the technology.This poster presents the results of the LCA based on the lab experiments for this wood-based high gravity process under development. Comparisons are made with wood-based ethanol production using a fermentation process at lower solids content, and with ethanol production using first-generation feedstocks and technology. LCA is thus used during the process development and may potentially have a significant influence on this development, and therefore on the sustainability of 2nd generation biofuels that are produced with a high gravity production process.
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| 2. |
- Janssen, Mathias, 1973, et al.
(författare)
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Life cycle impacts of ethanol production from spruce wood chips under high gravity conditions
- 2016
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834 .- 1754-6834. ; 9:1, s. 53-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundDevelopment of more sustainable biofuel production processes is ongoing, and technology to run these processes at a high dry matter content, also called high-gravity conditions, is one option. This paper presents the results of a life cycle assessment (LCA) of such a technology currently in development for the production of bio-ethanol from spruce wood chips.ResultsThe cradle-to-gate LCA used lab results from a set of 30 experiments (or process configurations) in which the main process variable was the detoxification strategy applied to the pretreated feedstock material. The results of the assessment show that a process configuration, in which washing of the pretreated slurry is the detoxification strategy, leads to the lowest environmental impact of the process. Enzyme production and use are the main contributors to the environmental impact in all process configurations, and strategies to significantly reduce this contribution are enzyme recycling and on-site enzyme production. Furthermore, a strong linear correlation between the ethanol yield of a configuration and its environmental impact is demonstrated, and the selected environmental impacts show a very strong cross-correlation (r^2 > 0.9 in all cases) which may be used to reduce the number of impact categories considered from four to one (in this case, global warming potential). Lastly, a comparison with results of an LCA of ethanol production under high-gravity conditions using wheat straw shows that the environmental performance does not significantly differ when using spruce wood chips. For this comparison, it is shown that eutrophication potential also needs to be considered due to the fertilizer use in wheat cultivation.ConclusionsThe LCA points out the environmental hotspots in the ethanol production process, and thus provides input to the further development of the high-gravity technology. Reducing the number of impact categories based only on cross-correlations should be done with caution. Knowledge of the analyzed system provides further input to the choice of impact categories.
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| 3. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Toward a sustainable biorefinery using high-gravity technology
- 2017
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Ingår i: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-1031 .- 1932-104X. ; 11:1, s. 15-27
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Tidskriftsartikel (refereegranskat)abstract
- The realization of process solutions for a sustainable bioeconomy depends on the efficient processing of biomass. High-gravity technology is one important alternative to realizing such solutions. The aims of this work were to expand the knowledge-base on lignocellulosic bioconversion processes at high solids content, to advance the current technologies for production of second-generation liquid biofuels, to evaluate the environmental impact of the proposed process by using life cycle assessment (LCA), and to develop and present a technically, economically, and environmentally sound process at high gravity, i.e., a process operating at the highest possible concentrations of raw material. The results and opinions presented here are the result of a Nordic collaborative study within the framework of the HG Biofuels project. Processes with bioethanol or biobutanol as target products were studied using wheat straw and spruce as interesting Nordic raw materials. During the project, the main scientific, economic, and technical challenges of such a process were identified. Integrated solutions to these challenges were proposed and tested experimentally, using wheat straw and spruce wood at a dry matter content of 30% (w/w) as model substrates. The LCA performed revealed the environmental impact of each of the process steps, highlighting the importance of the enzyme dose used for the hydrolysis of the plant biomass, as well as the importance of the fermentation yield.
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| 4. |
- Franzén, Carl Johan, 1966, et al.
(författare)
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Multifeed simultaneous saccharification and fermentation enables high gravity submerged fermentation of lignocellulose.
- 2015
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Ingår i: Recent Advances in Fermentation Technology (RAFT 11), Clearwater Beach, Florida, USA, November 8-11, 2015. Oral presentation..
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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.
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| 5. |
- Johansson, Emma, 1979, et al.
(författare)
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Fermentation performance and physiology of two strains of Saccharomyces cerevisiae during growth in high gravity spruce hydrolysate and spent sulphite liquor
- 2014
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Ingår i: BMC Biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 14, s. Art. no. 47-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lignocellulosic materials are a diverse group of substrates that are generally scarce in nutrients, which compromises the tolerance and fermentation performance of the fermenting organism. The problem is exacerbated by harsh pre-treatment, which introduces sugars and substances inhibitory to yeast metabolism. This study compares the fermentation behaviours of two yeast strains using different types of lignocellulosic substrates; high gravity dilute acid spruce hydrolysate (SH) and spent sulphite liquor (SSL), in the absence and presence of yeast extract. To this end, the fermentation performance, energy status and fermentation capacity of the strains were measured under different growth conditions. Results: Nutrient supplementation with yeast extract increased sugar uptake, cell growth and ethanol production in all tested fermentation conditions, but had little or no effect on the energy status, irrespective of media. Nutrient-supplemented medium enhanced the fermentation capacity of harvested cells, indicating that cell viability and reusability was increased by nutrient addition. Conclusions: Although both substrates belong to the lignocellulosic spruce hydrolysates, their differences offer specific challenges and the overall yields and productivities largely depend on choice of fermenting strain.
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| 6. |
- Koppram, Rakesh, 1986, et al.
(författare)
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Lignocellulosic ethanol production at high-gravity: Challenges and perspectives
- 2014
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Ingår i: Trends in Biotechnology. - : Elsevier BV. - 0167-7799 .- 1879-3096. ; 32:1, s. 46-53
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Forskningsöversikt (refereegranskat)abstract
- In brewing and ethanol-based biofuel industries, high-gravity fermentation produces 10-15% (v/v) ethanol, resulting in improved overall productivity, reduced capital cost, and reduced energy input compared to processing at normal gravity. High-gravity technology ensures a successful implementation of cellulose to ethanol conversion as a cost-competitive process. Implementation of such technologies is possible if all process steps can be performed at high biomass concentrations. This review focuses on challenges and technological efforts in processing at high-gravity conditions and how these conditions influence the physiology and metabolism of fermenting microorganisms, the action of enzymes, and other process-related factors. Lignocellulosic materials add challenges compared to implemented processes due to high inhibitors content and the physical properties of these materials at high gravity. © 2013 Elsevier Ltd.
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| 7. |
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| 8. |
- Paschos, T., et al.
(författare)
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Ethanol effect on metabolic activity of the ethalogenic fungus Fusarium oxysporum
- 2015
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Ingår i: BMC Biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Fusarium oxysporum is a filamentous fungus which has attracted a lot of scientific interest not only due to its ability to produce a variety of lignocellulolytic enzymes, but also because it is able to ferment both hexoses and pentoses to ethanol. Although this fungus has been studied a lot as a cell factory, regarding applications for the production of bioethanol and other high added value products, no systematic study has been performed concerning its ethanol tolerance levels. Results: In aerobic conditions it was shown that both the biomass production and the specific growth rate were affected by the presence of ethanol. The maximum allowable ethanol concentration, above which cells could not grow, was predicted to be 72 g/L. Under limited aeration conditions the ethanol-producing capability of the cells was completely inhibited at 50 g/L ethanol. The lignocellulolytic enzymatic activities were affected to a lesser extent by the presence of ethanol, while the ethanol inhibitory effect appears to be more severe at elevated temperatures. Moreover, when the produced ethanol was partially removed from the broth, it led to an increase in fermenting ability of the fungus up to 22.5%. The addition of F. oxysporum's system was shown to increase the fermentation of pretreated wheat straw by 11%, in co-fermentation with Saccharomyces cerevisiae. Conclusions: The assessment of ethanol tolerance levels of F. oxysporum on aerobic growth, on lignocellulolytic activities and on fermentative performance confirmed its biotechnological potential for the production of bioethanol. The cellulolytic and xylanolytic enzymes of this fungus could be exploited within the biorefinery concept as their ethanol resistance is similar to that of the commercial enzymes broadly used in large scale fermentations and therefore, may substantially contribute to a rational design of a bioconversion process involving F. oxysporum. The SSCF experiments on liquefied wheat straw rich in hemicellulose indicated that the contribution of the metabolic system of F. oxysporum in a co-fermentation with S. cerevisiae may play a secondary role.
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| 9. |
- Svensson, Elin, 1980, et al.
(författare)
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The effect of high solids loading in ethanol production integrated with a pulp mill
- 2016
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 111, s. 387-402
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, two ethanol processes integrated with a softwood pulp mill are compared with regard to their steam demand, process integration potential and profitability. The processes differ in the solids loading in the simultaneous saccharification and fermentation step and in the resulting ethanol concentration. The results show that a higher ethanol concentration does not necessarily lead to significant reductions in steam demand. Instead, it is demonstrated that the steam demand for distillation is highly dependent on the design of the distillation plant. Nevertheless, a higher solids loading (high gravity) can be beneficial for the treatment of the stillage from the distillation plant. A higher solids loading results either in a lower steam demand for evaporation of the stillage or possibly in a reduced demand for effluent treatment compared to a conventional solids loading process. While the results show that a higher ethanol concentration leads to advantages in energy costs and investment costs for the distillation plant, they also show that the potential benefits of a high-gravity process are offset by the expected decrease in ethanol yield, which leads to higher raw material costs. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Biotechnological potential of brewers spent grain and its recent applications
- 2012
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Ingår i: Waste and Biomass Valorization. - : Springer Science and Business Media LLC. - 1877-2641 .- 1877-265X. ; 3:2, s. 213-232
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Forskningsöversikt (refereegranskat)abstract
- Purpose Brewers spent grain (BSG) is a by-product of the brewing process corresponding to around 85% of total by-products generated. The great number of publications over the last 5 years, on the biotechnological applications of BSG, represents the increased scientific interest on it. This critical, state of the art review aims at gathering and analysing the most recent scientific efforts on the biotechnological potential of Brewer's spent grain and on its evaluation as a feedstock for high added value products. Methods The assiduous bibliographic retrospection focused on the latest scientific reports. The consideration of all relevant scientific articles was thorough and critical. The classification of the scientific efforts was made not only according to the end-products but also according to the biotechnological approach adopted. Results BSG has been used in a wide range of biotechnological applications such as substrate for enzymes production, as a source for value-added products (antioxidants, monosaccharides, oligosaccharides, xylitol, arabitol, bioethanol, biogas or lactic acid) or for the production of functional proteins and lipids. Its applications as a carrier in various bioprocesses have also been reported. Conclusion The implementation of BSG's fractionation in industrial scale seems to be the next step in BSG's exploitation. A fractionation process which allows the exploitation of biomolecules belonging to different classes, produced from one feedstock (BSG) may be used as a pattern for the implementation of the biorefinery concept in industrial scale, as long as the methods adopted ensure the functionality of the potentially valuable components.
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| 16. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Comparison of strategies to overcome the inhibitory effects in high-gravity fermentation of lignocellulosic hydrolysates
- 2014
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 65, s. 79-90
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Tidskriftsartikel (refereegranskat)abstract
- High-gravity (HG) technology aims at generating final ethanol concentrations above 50 kg m(-3) in order to reduce the cost of the distillation step. The generation of higher amounts of inhibitors during the pretreatment step is one of the challenges that accompany the increase in initial dry matter. Detoxification of spruce hydrolysate, adaptation of the cells before fermentation, supplementation with nutrients, and washing of solids were the strategies compared in this study. They represent different approaches to cope with the inhibitory effects, and we compared their efficiencies using a thermotolerant strain of Saccharomyces cereuisiae at temperatures from 30 degrees C up to 40 degrees C. The dilute acid-pretreated spruce used as substrate in this study was not fermentable under HG conditions (200 g kg(-1) water-insoluble solids) when no improvement method was applied. In HG simultaneous saccharification and fermentation at 30 degrees C combined with a 24 h pre-hydrolysis step, the detoxification of pretreated spruce with reducing agent (Na2S2O4) gave the best result with an ethanol yield of 57% (on total sugars) of the maximum theoretical and a volumetric productivity of 1.58 g dm(-3) h(-1). In HG separate hydrolysis and fermentation, nutrients supplementation gave better final ethanol yields than detoxification of the material, reaching an ethanol yield of about 60% of the theoretical (on total sugars). The results obtained, showed an increase in severity of inhibitory effects with temperature increase. Improved cell viability was observed when detoxified material was used and also when yeast extract addition was coupled with adaptation of the cells to the hydrolysate. (C) 2014 Published by Elsevier Ltd.
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| 17. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Evaluation of different strategies to overcome the inhibitory effects at high gravity processes using multivariate data analysis (MVDA)
- 2014
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Ingår i: Lignobiotech III, October 26-29, 2014, Concepcion, Chile.
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Konferensbidrag (refereegranskat)abstract
- High-gravity (HG) technology aims at generating final ethanol concentrations above 50 kg m3 in order to reduce the cost of the distillation step. The generation of higher amounts of inhibitors during the pretreatment step is one of the challenges that accom-pany the increase in initial dry matter. Detoxification of spruce hydrolysate, adaptation of the cells before fermentation, supplementation with nutrients, and washing of solids were the strategies compared in this study. They represent different approaches tocope with the inhibitory effects, and we compared their efficiencies using a thermotolerant strain of Saccharomyces cerevisiae at temperatures from 30oC up to 40oC.The dilute acid-pretreated spruce used as substrate in this study was not fermentable under HG conditions (200 g kg-1water-insoluble solids) when no improvement method was applied. In HG simultaneous saccharification and fermentationat 30oC combined with a 24 h pre-hydrolysis step, the detoxification of pretreated spruce with reducing agent (Na2S2O4) gave the best result with an ethanol yield of 57% (on total sugars) of the maximum theoretical and a volumetric productivity of1.58 g dm3 h−1. In HG separate hydrolysis and fermentation, nutrients supplementation gave better final ethanol yields than detoxification of the material, reaching an ethanol yield of about 60% of the theoretical (on total sugars). The results obtained, showed an increase in severity of inhibitory effects with temperature increase. Improved cell viability was observed when detoxified material was used and also when yeast extract addition was coupled with adaptation of the cells to the hydrolysate. The different fractions of hydrolysates after the application of different treatments were characterised and analysed using MVDA in order to evaluate the differences observed.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Hydrolysis and fermentation for cellulosic ethanol production
- 2013
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Ingår i: Wiley Interdisciplinary Reviews. - : Wiley. - 2041-8396 .- 2041-840X. ; 2:6, s. 633-654
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Tidskriftsartikel (refereegranskat)abstract
- Second-generation bioethanol produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, has the potential to be a valuable substitute for, or a complement to, gasoline. At least three major factors—rapidly increasing atmospheric CO2 levels, dwindling fossil fuel reserves, and their rising costs—suggest that we now need to accelerate research plans to make greater use of plant-based biomass for energy production and as a chemical feedstock as part of a sustainable energy economy. Optimizing the production of bioethanol to be competitive with petrochemical fuels is the main challenge for the underlying process development. The exhaustive research on enzyme technology during the latest years, resulting in significant advances in the field, show the importance of the enzymatic hydrolysis for a profitable ethanol production process. On the other hand, the persisting challenges in biomass pretreatment, which are the initial steps in most process designs, show the remarkable recalcitrance of the lignocellulosic materials to biological degradation. The recent scientific trends show toward an integrated overall bioconversion process in which fermentation technology and genetic engineering of ethanologenic microorganisms aim not only at maximizing yields and productivities but also at widening the range of fermentation products and applications.
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| 22. |
- Xiros, Charilaos, 1973, et al.
(författare)
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Hydrolysis and Fermentation for Cellulosic Ethanol Production
- 2015
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Ingår i: Advances in Bioenergy: The Sustainability Challenge. - Oxford, UK : John Wiley & Sons, Ltd. ; , s. 11-31, s. 11-31
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter summarizes the hydrolysis technologies and bioconversion processes employed for cellulosic ethanol production. Hydrolysis process involves pre-treatment methods (first-stage hydrolysis) and enzymatic hydrolysis (second-stage hydrolysis). Although cellulose is mainly present as crystalline fibers that are highly resistant to hydrolysis, its content in biomass is typically larger compared to hemicellulose and, as a result, cellulases are the key enzymes for bioethanol production. The major bioconversion processes are: The separate (or sequential) hydrolysis and fermentation (SHF), the simultaneous saccharification and fermentation (SSF) and the consolidated bioconversion process (CBP). Many yeast species have been reported to convert simple sugars to ethanol under anaerobic conditions. S. cerevisiae, Pichia stipitis, P. kudriavzevii (Candida krusei), Kluveromyces marxianus, C. shehatae, C. tropicalis, C. guilliermondii, and Pachysolen tannophilus are among the most often used yeast species in biomass-derived sugars-to-ethanol conversion processes.
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| 23. |
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