Engineering Zymomonas Mobilis for Efficient Fuel Ethanol Production from Lignocellulosic Feedstocks PDF Download
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Languages : en
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Author: Manoj Agrawal
Publisher:
ISBN:
Category : Anaerobic bacteria
Languages : en
Pages :
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Ethanol from lignocellulosic biomass is a promising alternative to rapidly depleting oil reserves. However, natural recalcitrance of lignocelluloses to biological and chemical treatments presents major engineering challenges in designing an ethanol conversion process. Current methods for pretreatment and hydrolysis of lignocelluloses generate a mixture of pentose (C5) and hexose (C6) sugars, and several microbial growth inhibitors such as acetic acid and phenolic compounds. Hence, an efficient ethanol production process requires a fermenting microorganism not only capable of converting mixed sugars to ethanol with high yield and productivity, but also having high tolerance to inhibitors. Although recombinant bacteria and yeast strains have been developed, ethanol yield and productivity from C5 sugars in the presence of inhibitors remain low and need to be further improved for a commercial ethanol production. The overarching objective of this work is to transform Zymomonas mobilis into an efficient whole-cell biocatalyst for ethanol production from lignocelluloses. Z. mobilis, a natural ethanologen, is ideal for this application but xylose (a C5 sugar) is not its 'natural' substrate. Back in 1995, researches at National Renewable Energy Laboratory (NREL) had managed to overcome this obstacle by metabolically engineering Z. mobilis to utilize xylose. However, even after more than a decade of research, xylose fermentation by Z. mobilis is still inefficient compared to that of glucose. For example, volumetric productivity of ethanol from xylose fermentation is 3- to 4- fold lower than that from glucose fermentation. Further reduction or complete inhibition of xylose fermentation occurs under adverse conditions. Also, high concentrations of xylose do not get metabolized completely. Thus, improvement in xylose fermentation by Z. mobilis is required. In this work, xylose fermentation in a metabolically engineered Z. mobilis was markedly improved by applying the technique of adaptive mutation. The adapted strain was able to grow on 10% (w/v) xylose and rapidly ferment xylose to ethanol within 2 days and retained high ethanol yield. Similarly, in mixed glucose-xylose fermentation, the strain produced a total of 9% (w/v) ethanol from two doses of 5% glucose and 5% xylose (or a total of 10% glucose and 10% xylose). Investigation was done to identify the molecular basis for efficient biocatalysis. An altered xylitol metabolism with reduced xylitol formation, increased xylitol tolerance and higher xylose isomerase activity were found to contribute towards improvement in xylose fermentation. Lower xylitol production in adapted strain was due to a single mutation in ZMO0976 gene, which drastically lowered the reductase activity of ZMO0976 protein. ZMO0976 was characterized as a novel aldo-keto reductase capable of reducing xylose, xylulose, benzaldehyde, furfural, 5-hydroxymethyl furfural, and acetaldehyde, but not glucose or fructose. It exhibited nearly 150-times higher affinity with benzaldehyde than xylose. Knockout of ZMO0976 was found to facilitate the establishment of xylose fermentation in Z. mobilis ZM4. Equipped with molecular level understanding of the biocatalytic process and insight into Z. mobilis central carbon metabolism, further genetic engineering of Z. mobilis was undertaken to improve the fermentation of sugars and lignocellulosic hydrolysates. These efforts culminated in construction of a strain capable of fermenting glucose-xylose mixture in presence of high concentration of acetic acid and another strain with a partially operational EMP pathway.
Author: Thalita Peixoto Basso
Publisher: BoD – Books on Demand
ISBN: 1789849373
Category : Science
Languages : en
Pages : 232
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This book offers a broad understanding of bioethanol production from sugarcane, although a few other substrates, except corn, will also be mentioned. The 10 chapters are grouped in five sections. The Fuel Ethanol Production from Sugarcane in Brazil section consists of two chapters dealing with the first-generation ethanol Brazilian industrial process. The Strategies for Sugarcane Bagasse Pretreatment section deals with emerging physicochemical methods for biomass pretreatment, and the non-conventional biomass source for lignocellulosic ethanol production addresses the potential of weed biomass as alternative feedstock. In the Recent Approaches for Increasing Fermentation Efficiency of Lignocellulosic Ethanol section, potential and research progress using thermophile bacteria and yeasts is presented, taking advantage of microorganisms involved in consolidating or simultaneous hydrolysis and fermentation processes. Finally, the Recent Advances in Ethanol Fermentation section presents the use of cold plasma and hydrostatic pressure to increase ethanol production efficiency. Also in this section the use of metabolic-engineered autotrophic cyanobacteria to produce ethanol from carbon dioxide is mentioned.
Author: Vincenza Faraco
Publisher: Springer Science & Business Media
ISBN: 3642378617
Category : Science
Languages : en
Pages : 207
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Bioethanol has been recognized as a potential alternative to petroleum-derived transportation fuels. Even if cellulosic biomass is less expensive than corn and sugarcane, the higher costs for its conversion make the near-term price of cellulosic ethanol higher than that of corn ethanol and even more than that of sugarcane ethanol. Conventional process for bioethanol production from lignocellulose includes a chemical/physical pre-treatment of lignocellulose for lignin removal, mostly based on auto hydrolysis and acid hydrolysis, followed by saccharification of the free accessible cellulose portions of the biomass. The highest yields of fermentable sugars from cellulose portion are achieved by means of enzymatic hydrolysis, currently carried out using a mix of cellulases from the fungus Trichoderma reesei. Reduction of (hemi)cellulases production costs is strongly required to increase competitiveness of second generation bioethanol production. The final step is the fermentation of sugars obtained from saccharification, typically performed by the yeast Saccharomyces cerevisiae. The current process is optimized for 6-carbon sugars fermentation, since most of yeasts cannot ferment 5-carbon sugars. Thus, research is aimed at exploring new engineered yeasts abilities to co-ferment 5- and 6-carbon sugars. Among the main routes to advance cellulosic ethanol, consolidate bio-processing, namely direct conversion of biomass into ethanol by a genetically modified microbes, holds tremendous potential to reduce ethanol production costs. Finally, the use of all the components of lignocellulose to produce a large spectra of biobased products is another challenge for further improving competitiveness of second generation bioethanol production, developing a biorefinery.
Author: C.A. Cardona
Publisher: CRC Press
ISBN: 1439815984
Category : Science
Languages : en
Pages : 418
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Book Description
Process engineering can potentially provide the means to develop economically viable and environmentally friendly technologies for the production of fuel ethanol. Focusing on a key tool of process engineering, Process Synthesis for Fuel Ethanol Production is a comprehensive guide to the design and analysis of the most advanced technologies for fuel
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Languages : en
Pages : 15
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To develop pathways for advanced biofuel production, and to understand the impact of host metabolism and environmental conditions on heterologous pathway engineering for economic advanced biofuels production from biomass, we seek to redirect the carbon flow of the model ethanologen Zymomonas mobilis to produce desirable hydrocarbon intermediate 2,3-butanediol (2,3-BDO). 2,3-BDO is a bulk chemical building block, and can be upgraded in high yields to gasoline, diesel, and jet fuel. 2,3-BDO biosynthesis pathways from various bacterial species were examined, which include three genes encoding acetolactate synthase, acetolactate decarboxylase, and butanediol dehydrogenase. Bioinformatics analysis was carried out to pinpoint potential bottlenecks for high 2,3-BDO production. Different combinations of 2,3-BDO biosynthesis metabolic pathways using genes from different bacterial species have been constructed. Our results demonstrated that carbon flux can be deviated from ethanol production into 2,3-BDO biosynthesis, and all three heterologous genes are essential to efficiently redirect pyruvate from ethanol production for high 2,3-BDO production in Z. mobilis. The down-selection of best gene combinations up to now enabled Z. mobilis to reach the 2,3-BDO production of more than 10 g/L from glucose and xylose, as well as mixed C6/C5 sugar streams derived from the deacetylation and mechanical refining process. In conclusion, this study confirms the value of integrating bioinformatics analysis and systems biology data during metabolic engineering endeavors, provides guidance for value-added chemical production in Z. mobilis, and reveals the interactions between host metabolism, oxygen levels, and a heterologous 2,3-BDO biosynthesis pathway. Taken together, this work provides guidance for future metabolic engineering efforts aimed at boosting 2,3-BDO titer anaerobically.
Author: Ayerim Y. Hernández Almanza
Publisher: CRC Press
ISBN: 1000565130
Category : Science
Languages : en
Pages : 542
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Book Description
This new book, Bioethanol: Biochemistry and Biotechnological Advances, presents some insightful perspectives and important advances in the bioethanol industry. The volume goes into detail on the biochemical and physiological parameters carried out by the main bioethanol-producing microorganisms as well as the discusses the potential applications that bioproducts can have and the advantages they generate. The chapter authors discuss a variety of issues, including the physiology of ethanol production by yeasts, by Zymomonas mobilis, and by Clostridium thermocellum. Other sources of biofuel, such as sweet sorghum, Agave americana L. leaves waste, and fungi are included as well. Chapters also discuss the genetic regulation and genetic engineering of principal microorganisms and then go on to address ways to increase ethanol tolerance in industrially important ethanol fermenting organisms, methods for developing sustainable fermentable substrates, and new strategies for ethanol purification. Chapters explore the design and engineering requirements for bioreactors, bioelectrosynthesis of ethanol via bioelectrochemical systems, and more. The book will be a valuable resource for faculty and students in this area as well as for scientists, researchers, and managers in the biofuel industry in the area of biofuel production, fermentation process, environmental engineering and all other related scientific areas.
Author: Charles Wyman
Publisher: Routledge
ISBN: 1351441760
Category : Technology & Engineering
Languages : en
Pages : 289
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Book Description
Bioethanol is a versatile transportation fuel and fuel additive that offers excellent performance and reduced air pollution compared to conventional fuels. Its production and use adds little, if any, net release of carbon dioxide to the atmosphere, dramatically reducing the potential for global climate change. Through a sustained research program and an emerging economic competitiveness, the technology for bioethanol production is poised for immediate widespread commercial applications. Written by engineers and scientists providing a technical focus, this handbook provides the up-to-date information needed by managers, engineers, and scientists to evaluate the technology, market, and economics of this fuel, while examining the development of production required to support its commercial use.
Author: Xin Lu
Publisher: Woodhead Publishing
ISBN: 0128188634
Category : Technology & Engineering
Languages : en
Pages : 268
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Book Description
Advances in 2nd Generation of Bioethanol Production presents a comprehensive overview of technologies and strategies for the conversion of lignocellulosic biomass. This includes issues like sustainable production, environmental and economic benefits, and the main hurdles for upscaling and achieving commercial viability. The book assesses the current biomass conversion technologies, their readiness level for commercial production, and applications of bioethanol in bioenergy and chemical feedstock. The essential conversion process of 2nd generation biofuels, including feedstock composition and pretreatment, is then broken down, with special focus on advantages and pitfalls of each feedstock and process. It also explores the advances and challenges of bioprocessing, hydrolysis technologies and simultaneous fermentation of pentose and hexose. Finally, it presents the current status and bottlenecks for industrial production of bioethanol, as well as its future prospects. Its interdisciplinary approach, drawing upon plant biology, chemistry, biochemistry, microbiology, and genetics, makes Advances in 2nd Generation of Bioethanol Production a must-have reference for researchers in academia and industry R&D. It allows them to compare challenges and opportunities of new technologies and identify the gaps where new technology is needed. Practitioners in the industry also benefit from the information on working principles, design and control of the bioethanol production process, highlighting areas where technology innovation and investment should be placed. Graduate students and researchers newly entered in this field find here a key-resource to thoroughly understand the process as well as the fundamentals of bioethanol and bioproducts production from lignocellulosic biomass. - Presents fundamentals and state-of-the-art of available pathways for bioethanol and bioproducts production from lignocellulosic biomass - Discusses key-challenges for large scale production of bioethanol, such as pretreatment and hydrolysis - Covers the specificities of various feedstocks and processes, the role of microorganisms in fermentation, saccharification limitations and challenges in the C5 and C6 fermentation
