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RISS 인기검색어
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- 저자 : R. Axayácatl González-García (검색결과 2 건)
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R. Axayácatl González-García,E. Ines Garcia-Peña,Edgar Salgado-Manjarrez,Juan S. Aranda-Barradas 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.6
Increasing recombinant protein production yieldsfrom bacterial cultures remains an important challenge inbiotechnology. Acetate accumulation due to high dissolvedcarbon dioxide (pCO2) concentrations in the medium hasbeen identified as a factor that negatively affects suchyields. Under appropriate culture conditions, acetate couldbe re-assimilated by bacterial cells to maintain heterologousproteins production. In this work, we developed a simplifiedmetabolic network aiming to establish a reaction rate analysisfor a recombinant Escherichia coli when producing greenfluorescent protein (GFP) under controlled pCO2 concentrations. Because E. coli is able to consume both glucoseand acetate, the analysis was performed in two stages. Ourresults indicated that GFP synthesis is an independentprocess of cellular growth in some culture phases. Additionally,recombinant protein production is influenced bythe available carbon source and the amount of pCO2 in theculture medium. When growing on glucose, the increase inthe pCO2 concentration produced a down-regulation ofcentral carbon metabolism by directing the carbon fluxtoward acetate accumulation; as a result, cellular growthand the overall GFP yield decreased. However, the maximumspecific rate of GFP synthesis occurred with acetate as themain available carbon source, despite the low activity inthe other metabolic pathways. To maintain cellular functions,including GFP synthesis, carbon flux was re-distributedtoward the tricarboxylic acid cycle and the pentose phosphatepathway to produce ATP and NADH. The thermodynamicanalysis allowed demonstrating the feasibility of the simplifiednetwork for describing the metabolic state of a recombinantsystem.
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Iliana Barrera-Martinez,R. Axayácatl González-García,Edgar Salgado-Manjarrez,Juan S. Aranda-Barradas 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1
Production of Saccharomyces cerevisiae yeast for applications in the food industry or in bioethanol production still presents important techno-economic challenges as an industrial bioprocess. Mathematical modeling of cellular metabolism in biological production usually improves process yields, though for industrial applications,the model should be as simple as possible in order to sustain model usefulness and technical feasibility. A comparative analysis between a black box description and a simple metabolic network accounting for the main metabolic events involved in yeast growth and bioethanol production is proposed here. In both cases, a thorough analysis of reaction rates allowed for the ethanol concentrations produced in fed-batch yeast cultures, although our results showed more accurate estimations with the metabolic flux balance methodology. Moreover, an interpretation of the yeast physiological state in fed-batch cultures at different glucose feed concentrations was accomplished by means of a stoichiometric analysis linked to the simplified metabolic network. The results confirmed that increasing glucose uptake rates, controlled mainly by the glucose concentration in the input flow, produced an up-regulation in reductive catabolism, resulting in higher ethanol excretion. The biomass production relied mostly on oxidative catabolism,which is controlled by the glucose and oxygen uptake rates. Thus, ethanol or biomass production is strongly dependent on the physiological state of yeast in the culture, which can be inferred from a suitable metabolic flux balance approach.
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