Metabolic engineering of bacteria for ethanol production

Ingram, L. O.; Gomez, P. F.; Lai, Xiaokuang; Moniruzzaman, Mohammed; Wood, B. E.; Yomano, Lorraine P.; York, Sean W.

doi:10.1002/(sici)1097-0290(19980420)58:2/3<204::aid-bit13>3.3.co;2-p

Cited by 26 publications

(35 citation statements)

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“…These include: the removal of the enzyme or its inhibition to eliminate a competitive pathway (Green et al, 1996;Gasson et al, 1996;Shimada et al, 1998) or a toxic byproduct Cameron et al, 1998, Chaplen at al., 1996; the amplification of a gene or group of genes to improve the synthesis of existing products (Pines et al, 1997;Shimada et al, 1998;Lu and Liao;; the expression of an heterologous enzyme(s) to extend the substrate range (Prieto et al, 1996;Panke et al, 1998;Sprenger, 1996), to produce novel product (Chopra and Vageeshbabu, 1996;Hershberger, 1996;Ingram et al, 1998;Misawa and Shimada, 1998;Poirier et al, 1995;Stassi et al, 1998), to provide pathways for the degradation of toxic compounds (Chen and Wilson, 1997;Keasling et al, 1998;Xu et al, 1996), or to design a more environmentally resistant plant (Smirnoff, 1998). Alternatively, the deregulation of existing enzymes might be necessary to overcome the existing control mechanisms of a rigid node.…”

Section: Selection Of the Methods Of Genetic Modificationmentioning

confidence: 99%

Genetic and metabolic engineering

Yang¹,

Bennett²,

San³

1998

Electron. J. Biotechnol.

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Recent advances in molecular biology techniques, analytical methods and mathematical tools have led to a growing interest in using metabolic engineering to redirect metabolic fluxes for industrial and medical purposes. Metabolic engineering is referred to as the directed improvement of cellular properties through the modification of specific biochemical reactions or the introduction of new ones, with the use of recombinant DNA technology (Stephanopoulos, 1999). This multidisciplinary field draws principles from chemical engineering, biochemistry, molecular and cell biology, and computational sciences. The aim of this article is to give an overview of the various strategies and tools available for metabolic engineers and to review some of the recent work that has been conducted in our laboratories in the metabolic engineering area.Metabolic engineering is generally referred to as the targeted and purposeful alteration of metabolic pathways found in an organism in order to better understand and utilize cellular pathways for chemical transformation, energy transduction, and supramolecular assembly (Lessard, 1996). This multidisciplinary field draws principles from chemical engineering, computational sciences, biochemistry, and molecular biology. In essence, metabolic engineering is the application of engineering principles of design and analysis to the metabolic pathways in order to achieve a particular goal. This goal may be to increase process productivity, as in the case in production of antibiotics, biosynthetic precursors or polymers, or to extend metabolic capability by the addition of extrinsic activities for chemical production or degradation. Previous strategies to attain these goals seem more of an art with experimentation by trial-and-error. Two papers in the early 1990s advocated the switch from this artistic approach to a more systematic and rational approach (Bailey, 1991, Stephanopoulos and Vanillo, 1991). This scientific approach would involve the use of recombinant DNA technology and a better understanding of cellular physiology to modify intermediary metabolism. Several reviews on metabolic engineering cover general

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Section: Selection Of the Methods Of Genetic Modificationmentioning

confidence: 99%

Genetic and metabolic engineering

Yang¹,

Bennett²,

San³

1998

Electron. J. Biotechnol.

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“…At this concentration, ethanol recovery is relatively inexpensive and does not prevent such processes from having a very favorable overall energy balance [10]. Although xylose was not converted by the yeast used in this study, several xylose-utilizing ethanol-producing organisms have been developed [18,19,20]. It would be of interest to try one or more such organisms for semicontinuous conversion of paper sludge as xylan conversion has the potential to increase the ethanol yield by nearly 20% as compared to conversion of glucan only for the sludge we studied.…”

Section: Discussionmentioning

confidence: 99%

Conversion of paper sludge to ethanol in a semicontinuous solids-fed reactor

Zhang

South

Lyford

et al. 2003

Bioprocess and Biosystems Engineering

134

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Conversion of paper sludge to ethanol was investigated with the objective of operating under conditions approaching those expected of an industrial process. Major components of the bleached Kraft sludge studied were glucan (62 wt.%, dry basis), xylan (11.5%), and minerals (17%). Complete recovery of glucose during compositional analysis required two acid hydrolysis treatments rather than one. To avoid the difficulty of mixing unreacted paper sludge, a semicontinuous solids-fed laboratory bioreactor system was developed. The system featured feeding at 12-h intervals, a residence time of 4 days, and cellulase loading of 15 to 20 FPU/g cellulose. Sludge was converted to ethanol using simultaneous saccharification and fermentation (SSF) featuring a beta-glucosidase-supplemented commercial cellulase preparation and glucose fermentation by Saccharomyces cerevisiea. SSF was carried out for a period of 4 months in a first-generation system, resulting in an average ethanol concentration of 35 g/L. However, steady state was not achieved and operational difficulties were encountered. These difficulties were avoided in a retrofitted design that was operated for two 1-month runs, achieving steady state with good material balance closure. Run 1 with the retrofitted reactor produced 50 g/L ethanol at a cellulose conversion of 74%. Run 2 produced 42 g/L ethanol at a conversion of 92%. For run 2, the ethanol yield was 0.466 g ethanol/g glucose equivalent fermented and >94% of the xylan fed to the reactor was solubilized to a mixture of xylan oligomers and xylose.

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“…71 Posteriormente, os mesmos autores reportaram um estudo mais aprofundado sobre o organismo recombinante produzido, envolvendo a análise de seu fluxo metabólico, para o aumento da produtividade em etanol. 72 Mais recentemente, Zhou e colaboradores utilizaram a mesma bactéria, K. oxytoca, já contendo os genes de produção de etanol de Z. mobilis incorporados em seu cromossomo, como hospedeiro dos genes de síntese de endoglucanase de Erwinia chrysantemi, de forma a atuarem sinergicamente com b-glicosidase naturalmente ocorrente na bactéria hospedeira, permitindo que o micro-organismo recombinante gerado metabolizasse fontes celulósicas integralmente, gerando como produto etanol, em apenas uma etapa.…”

Section: Estudos Com Micro-organismos Geneticamente Modificados (Mgms)unclassified

Produção, propriedades e aplicação de celulases na hidrólise de resíduos agroindustriais

Castro¹,

Pereira²

2010

Quím. Nova

107

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Recebido em 13/5/09; aceito em 24/6/09; publicado na web em 25/11/09 PRODUCTION, PROPERTIES AND APPLICATION OF CELLULASES IN THE HYDROLYSIS OF AGROINDUSTRIAL RESIDUES. Cellulases have been intensively studied in the past few years, due to the interests in biofuels production from lignocellulosic materials, since they permit maintaining mild conditions during the conversion process. These enzymes can be produced by a broad variety of naturally occurring microorganisms, such as from genera Aspergillus, Trichoderma, Penicillium and Humicola. Targeting the increasing of expression levels, molecular biology tools have been used for heterologous genes insertion in host cells, e. g., Pichia pastoris and Escherichia coli. Enzymes from fungal cellulolytic complex usually act best at pH between 4 and 5 under temperatures from 40 to 60 °C and can be used for either sequential (SHF) or simultaneous (SSF) hydrolysis together alcoholic fermentation. In this review, the main raw materials for production of cellulases are identified, as well as the state of art of enzymes' properties, production and main applications.Keywords: cellulases; agroindustrial residues; lignocellulose. INTRODUÇÃOCelulases são enzimas que constituem um complexo capaz de atuar sobre materiais celulósicos, promovendo sua hidrólise. Estas enzimas são biocatalisadores altamente específicos que atuam em sinergia para a liberação de açúcares, dos quais glicose é o que desperta maior interesse industrial, devido à possibilidade de sua conversão em etanol. 1,2Estas enzimas começaram a ser estudadas durante a Segunda Guerra Mundial. A deterioração de fardas, barracas, bolsas e demais objetos dos acampamentos, fabricados de algodão, chamou a atenção de soldados das forças armadas norte-americanas, instalados nas ilhas Solomon, no Pacífico Sul. Algumas organizações, como a Quartermaster Corps, juntamente com as forças armadas, montaram laboratórios em busca de explicações e soluções imediatas para esse problema, que incluíam a detecção de organismos agentes das deteriorações, seus mecanismos de ação e métodos de controle. O grupo de trabalho, constituído por oito pesquisadores e liderado pelo Dr. Elwyn T. Reese, passou a conduzir seus experimentos no laboratório das forças armadas, em Natick, Massachusets, Estados Unidos. Como resultado das pesquisas, uma linhagem, codificada como QM6a, de um fungo filamentoso, identificado posteriormente como Trichoderma viride, foi isolada e a esta foi atribuída a característica de excretar enzimas capazes de degradar celulose. Até 1953, Dr. Reese e seu grupo de trabalho já haviam determinado que enzimas naturais, nomeadas celulases, constituem complexos de diversas moléculas com distintas habilidades na degradação do substrato. Em 1956, Dr. Reese aliou seus conhecimentos aos da Dra. Mary Mandels, que, em conjunto, passaram a trabalhar no laboratório em Natick. A partir de então, o foco das pesquisas deixou de ser a prevenção da hidrólise da celulose e passou a ser o melhoramento da produção das enzimas responsáveis por esse fe...

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Metabolic engineering of bacteria for ethanol production

Cited by 26 publications

References 0 publications

Genetic and metabolic engineering

Genetic and metabolic engineering

Conversion of paper sludge to ethanol in a semicontinuous solids-fed reactor

Produção, propriedades e aplicação de celulases na hidrólise de resíduos agroindustriais

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