Comparison of Different Strategies to Reduce Acetate Formation in Escherichia coli

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• 作者：Marjan De Mey ; Gaspard J. Lequeux ; Joeri J. Beauprez ; Jo Maertens ; Ellen Van Horen ; Wim K. Soetaert ; Peter A. Vanrolleghem ; Erick J. Vandamme
• 刊名：Biotechnology Progress
• 出版年：2007
• 出版时间：October 2007
• 年：2007
• 卷：23
• 期：5
• 页码：1053 - 1063
• 全文大小：368K
• 年卷期：v.23,no.5(October 2007)
• ISSN：1520-6033

文摘

E. coli cells produce acetate as an extracellular coproduct of aerobic cultures. Acetate isundesirable because it retards growth and inhibits protein formation. Most process designs orgenetic modifications to minimize acetate formation aim at balancing growth rate and oxygenconsumption. In this research, three genetic approaches to reduce acetate formation wereinvestigated: (1) direct reduction of the carbon flow to acetate (ackA-pta, poxB knock-out); (2)anticipation on the underlying metabolic and regulatory mechanisms that lead to acetate(constitutive ppc expression mutant); and (3) both (1) and (2). Initially, these mutants werecompared to the wild-type E. coli via batch cultures under aerobic conditions. Subsequently,these mutants were further characterized using metabolic flux analysis on continuous cultures.It is concluded that a combination of directly reducing the carbon flow to acetate and anticipatingon the underlying metabolic and regulatory mechanism that lead to acetate, is the most promisingapproach to overcome acetate formation and improve recombinant protein production. Thesegenetic modifications have no significant influence on the metabolism when growing the micro-organisms under steady state at relatively low dilution rates (less than 0.4 h^-1).