| 1. |
- Geijer, Cecilia, 1980, et al.
(författare)
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Characterization of a novel non-GMO yeast for future lignocellulosic bioethanol production
- 2014
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Ingår i: ISSY31: 31ST International Specialised Symposium on Yeast.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- CHARACTERIZATION OF A NOVEL NON-GMO YEAST FOR FUTURE LIGNOCELLULOSIC BIOETHANOL PRODUCTIONCecilia Geijer1, David Moreno1, Elia Tomas Pejo1, 2, Lisbeth Olsson11 Industrial Biotechnology , Department of Chemical and Biological Engineering Chalmers University of Technology, Gothenburg, Sweden2Unit of Biotechnological Processes for Energy Production, IMDEA Energy, Móstoles (Madrid), SpainContact details: cecilia.geijer@chalmers.seConcerns about climate change and the uncertainty about future fuel supply make renewable biofuels, such as bioethanol, attractive alternatives to fossil fuels in the short/medium term. Lignocellulosic biomass (for example spruce, wheat straw and corn stover) is an abundant raw material that can be utilized to produce ethanol with the help of a fermenting microorganism. Traditionally the yeast Saccharomyces cerevisiae is used for industrial ethanol production. S. cerevisiae can be metabolically engineered to consume xylose (the second to glucose most prevalent monosaccharide in lignocellulose). However, despite many years of intensive research, it can still not ferment xylose in a satisfying way which affects the overall ethanol yield negatively. We have isolated a non-genetically modified (non-GMO) yeast species (here called C5-yeast) that has the natural ability to efficiently produce ethanol from glucose and xylose. The aim of the project is to further characterize the growth and fermentation capacities of this novel microorganism to elucidate its’ potential for lignocellulosic bioethanol production. We can show that besides glucose and xylose, the C5-yeast can also consume the pentose arabinose and the disaccharide cellobiose; both present in lignocellulosic hydrolysates. The C5-yeast rapidly converts the inhibitory sugar degradation products HMF and furfural formed during the conversion of lignocellulosic material into fermentable sugars.
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| 2. |
- Geijer, Cecilia, 1980, et al.
(författare)
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Evolutionary engineered strains of Saccharomyces cerevisiae for efficient lignocellulosic bioethanol production
- 2014
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Ingår i: 36th Symposium on Biotechnology for Fuels and Chemicals.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lignocellulosic biomass is an abundant raw material that can be utilized to produce ethanol with the help of Saccharomyces cerevisiae; a promising alternative to today’s energy sources. Conversion of lignocellulosic material (cellulose, hemicellulose and lignin) into fermentable sugars including both hexoses and pentoses results in formation of inhibitory compounds such as acetic acid, furan aldehydes and phenolics that are known to inhibit the yeasts’ metabolic processes. The aims of this study were to i) generate S. cerevisiae strains that can readily convert glucose and xylose into ethanol in the presence of inhibitory compounds, and ii) elucidate the underlying genetic changes of importance for the improved properties of the generated strains. For these purposes, a strain of S. cerevisiae containing genes for xylose reductase, xylitol dehydrogenase and xylulokinase was used. The strain was subjected to mutagenesis followed by evolutionary engineering (repetitive batch and chemostat cultivation), which resulted in populations with improved ethanol yield, improved xylose conversion rate and increased inhibitor tolerance. The complex combination of different genetic alterations in the evolved populations will now be revealed using a DNA/RNA sequencing approach. The acquired knowledge of proteins and pathways important for efficient lignocellulosic bioethanol production will then hopefully allow directed engineering for further improvement of yeast performance.
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| 3. |
- Geijer, Cecilia, 1980, et al.
(författare)
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Unraveling the potential of non-conventional yeasts in biotechnology
- 2022
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- Cost-effective microbial conversion processes of renewable feedstock into biofuels and biochemicals are of utmost importance for the establishment of a robust bioeconomy. Conventional baker's yeast Saccharomyces cerevisiae, widely employed in biotechnology for decades, lacks many of the desired traits for such bioprocesses like utilization of complex carbon sources or low tolerance towards challenging conditions. Many non-conventional yeasts (NCY) present these capabilities, and they are therefore forecasted to play key roles in future biotechnological production processes. For successful implementation of NCY in biotechnology, several challenges including generation of alternative carbon sources, development of tailored NCY and optimization of the fermentation conditions are crucial for maximizing bioproduct yields and titers. Addressing these challenges requires a multidisciplinary approach that is facilitated through the 'YEAST4BIO' COST action. YEAST4BIO fosters integrative investigations aimed at filling knowledge gaps and excelling research and innovation, which can improve biotechnological conversion processes from renewable resources to mitigate climate change and boost transition towards a circular bioeconomy. In this perspective, the main challenges and research efforts within YEAST4BIO are discussed, highlighting the importance of collaboration and knowledge exchange for progression in this research field.
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| 4. |
- Moreno, A. D., et al.
(författare)
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Candida intermedia CBS 141442: A novel glucose/xylose co-fermenting isolate for lignocellulosic bioethanol production
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:20
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Tidskriftsartikel (refereegranskat)abstract
- The present study describes the isolation of the novel strain Candida intermedia CBS 141442 and investigates the potential of this microorganism for the conversion of lignocellulosic streams. Different C. intermedia clones were isolated during an adaptive laboratory evolution experiment under the selection pressure of lignocellulosic hydrolysate and in strong competition with industrial, xylose-fermenting Saccharomyces cerevisiae cells. Isolates showed different but stable colony and cell morphologies when growing in a solid agar medium (smooth, intermediate and complex morphology) and liquid medium (unicellular, aggregates and pseudohyphal morphology). Clones of the same morphology showed similar fermentation patterns, and the C. intermedia clone I5 (CBS 141442) was selected for further testing due to its superior capacity for xylose consumption (90% of the initial xylose concentration within 72 h) and the highest ethanol yields (0.25 ± 0.02 g ethanol/g sugars consumed). Compared to the well-known yeast Scheffersomyces stipitis, the selected strain showed slightly higher tolerance to the lignocellulosic-derived inhibitors when fermenting a wheat straw hydrolysate. Furthermore, its higher glucose consumption rates (compared to S. stipitis) and its capacity for glucose and xylose co-fermentation makes C. intermedia CBS 141442 an attractive microorganism for the conversion of lignocellulosic substrates, as demonstrated in simultaneous saccharification and fermentation processes.
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| 5. |
- Moreno, David, 1986, et al.
(författare)
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An engineered Saccharomyces cerevisiae for cost-effective lignocellulosic bioethanol production: process performance and physiological insights
- 2015
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Ingår i: 37th Symposium on Biotechnology for Fuels and Chemicals.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The success in the commercialization of lignocellulosic bioethanol relies on the development of microorganisms with efficient hexose and pentose fermentation and tolerance towards inhibitory by-products (acetic acid, furan aldehydes and phenolics) generated during biomass processing. Traditionally, the yeast Saccharomyces cerevisiae is the preferred microorganism for industrial ethanol production. Many years of research and development have been conducted to develop S. cerevisiae strains suitable for fermenting lignocellulosic-based streams. S. cerevisiae is robust and ferment glucose efficiently, but it has been proved to be difficult to genetically modify for efficient xylose fermentation. In this work, a xylose-fermenting S. cerevisiae strain was subjected to evolutionary engineering, boosting its robustness and xylose fermentation capacity. The evolved strain was able to ferment a non-diluted enzymatic hydrolysate (representing 23% (w/w) dry matter of steam-exploded wheat straw), reaching ethanol titers higher than 5% (w/w) after 48 h. Within the first 24 h, glucose and xylose were co-consumed with rates of 3.1 and 0.7 g/L h, respectively, and converted to ethanol with yields corresponding to 93% of the theoretical. In addition, once glucose was depleted, xylose was consumed with a similar rate until reducing 70% of its initial concentration (36 h after inoculation). Besides investigating the fermentation parameters, the differences in gene expression levels and enzymatic activities of xylose-assimilating pathway were analyzed. These analyses will be the foundation for understanding the improved phenotype and the physiological mechanisms for efficient xylose fermentation, after which potential targets for subsequent metabolic engineering may be identified.
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| 6. |
- Moreno, David, 1986, et al.
(författare)
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Isolation and evolution of a novel non-saccharomyces xylose-fermenting strain for lignocellulosic bioethanol production
- 2014
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Ingår i: ISSY31: 31ST International Specialised Symposium on Yeast.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- ISOLATION AND EVOLUTION OF A NOVEL NON-SACCHAROMYCES XYLOSE-FERMENTING STRAIN FOR LIGNOCELLULOSIC BIOETHANOL PRODUCTIONAntonio D. Moreno1, Cecilia Geijer1, Elia Tomás-Pejó1,2, Lisbeth Olsson1.1Chalmers University of Technology, Department of Chemical and Biological Engineering, Industrial Biotechnology Group, Göteborg, Sweden. 2Unit of Biotechnological Processes for Energy Production, IMDEA Energy, Móstoles (Madrid), Spain.Contact e-mail: davidmo@chalmers.seThe economical success of lignocellulosic bioethanol requires the fermentation of all available sugars obtained during the process. Being the major pentose sugar in lignocellulose, the fermentation of xylose is, therefore, considered essential. The fermentative yeast Saccharomyces cerevisiae is the most promising candidate for lignocellulosic bioethanol production due to its excellent glucose fermentation capability, high ethanol tolerance and resistance to inhibitors presented in lignocellulosic streams. Nevertheless, the wild type S. cerevisae is not able to ferment xylose and all of the purpose-engineered Saccharomyces strains (genetically modified microorganisms (GMO)) are still far away from an economically viable lignocellulosic ethanol production. By chance, we have discovered a non-Saccharomyces xylose-fermenting yeast (here called C5-yeast), which shows a great potential to be used for bioethanol production from lignocellulosic streams. Unlike xylose-fermenting Saccharomyces strains, the C5-yeast is not genetically modified and its use by industries can aid in finding less legislative problems when reaching the market. In the present work, the C5-yeast was isolated from a xylose-fermenting population and evolutionary engineered to enhance its fermentation abilities and robustness. During the isolation process, three different morphologies (smooth, flat and wrinkled) of the C5-yeast were found when growing the xylose-fermenting population in plates with minimal media and xylose as a sole carbon source. Among all morphologies, flat-C5-yeast showed the highest xylose consumption rates (>90% after 72 h) and the highest ethanol conversion yields (≈50% of the theoretical considering glucose and xylose) during the fermentation of wheat straw hydrolysates. The isolated flat-C5-yeast was selected for evolutionary engineering in order to enhance its sugar conversion yields and the tolerance towards the inhibitory compounds that are present in the hydrolysate. Although further characterization is needed, an evolved C5-yeast could be considered as a suitable fermentative strain for lignocellulosic bioethanol production.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Moreno, A. D., et al.
(författare)
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A review of biological delignification and detoxification methods for lignocellulosic bioethanol production
- 2015
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Ingår i: Critical Reviews in Biotechnology. - : Informa UK Limited. - 0738-8551 .- 1549-7801. ; 35:3, s. 342-354
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Forskningsöversikt (refereegranskat)abstract
- Future biorefineries will integrate biomass conversion processes to produce fuels, power, heat and value-added chemicals. Due to its low price and wide distribution, lignocellulosic biomass is expected to play an important role toward this goal. Regarding renewable biofuel production, bioethanol from lignocellulosic feedstocks is considered the most feasible option for fossil fuels replacement since these raw materials do not compete with food or feed crops. In the overall process, lignin, the natural barrier of the lignocellulosic biomass, represents an important limiting factor in biomass digestibility. In order to reduce the recalcitrant structure of lignocellulose, biological pretreatments have been promoted as sustainable and environmentally friendly alternatives to traditional physico-chemical technologies, which are expensive and pollute the environment. These approaches include the use of diverse white-rot fungi and/or ligninolytic enzymes, which disrupt lignin polymers and facilitate the bioconversion of the sugar fraction into ethanol. As there is still no suitable biological pretreatment technology ready to scale up in an industrial context, white-rot fungi and/or ligninolytic enzymes have also been proposed to overcome, in a separated or in situ biodetoxification step, the effect of the inhibitors produced by non-biological pretreatments. The present work reviews the latest studies regarding the application of different microorganisms or enzymes as useful and environmentally friendly delignification and detoxification technologies for lignocellulosic biofuel production. This review also points out the main challenges and possible ways to make these technologies a reality for the bioethanol industry.
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| 10. |
- Moreno, David, 1986, et al.
(författare)
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Exploring laccase and mediators behavior during saccharification and fermentation of steam-exploded wheat straw for bioethanol production
- 2016
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 1097-4660 .- 0268-2575. ; 91:6, s. 1816-1825
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Laccases represent a very powerful tool to improve biorefining processes from lignocellulosic feedstocks. These enzymes are being investigated not only for potential use as pretreatment agents in bioethanol production, mainly as a delignifying agent, but also as a biotechnological tool for removal of inhibitors (mainly phenols) of subsequent fermentation processes. RESULTS: In this work, the treatment of the water insoluble solids (WIS) fraction from steam-exploded wheat straw with Pycnoporus cinnabarinus laccase and different laccase-mediator systems (LMS) did not decrease the lignin content, resulting in lower glucose recoveries during the subsequent saccharification. In combination with an alkaline extraction, the treatment with laccase/LMS produced no synergistic effect enhancing the delignification or saccharification of WIS. In contrast, laccase reduced the soluble phenols (95% of the total phenols identified) of the whole slurry from steam-exploded wheat straw, improving the yeast performance during the fermentation and enhancing the ethanol yields. CONCLUSIONS: The efficiency of P. cinnabarinus laccase with or without mediators as a delignifying agent on steam-exploded wheat straw for bioethanol production was not observed, whereas its detoxification ability was shown. Thus, new laccases or designing laccases with ability to delignify and detoxify simultaneously needs to be explored in order to produce major ethanol global yields.
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