Kinetic Modeling and Isotopic Investigation of Isobutanol Fermentation by Two Engineered Escherichia coli Strains

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• 作者：Yi Xiao ; Xueyang Feng ; Arul M. Varman ; Lian He ; Huifeng Yu ; Yinjie J. Tang
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2012
• 出版时间：December 12, 2012
• 年：2012
• 卷：51
• 期：49
• 页码：15855-15863
• 全文大小：497K
• 年卷期：v.51,no.49(December 12, 2012)
• ISSN：1520-5045

文摘

We constructed an Escherichia coli BL21 strain with the Ehrlich pathway (the low-performance strain for isobutanol production). We also obtained a high isobutanol-producing E. coli strain JCL260 from the James Liao group (University of California). To compare the fermentation performances of the two engineered strains, we employed a general Monod-based model coupled with mixed-growth-associated isobutanol formation kinetics to simulate glucose consumption, biomass growth, and product secretion/loss under different cultivation conditions. On the basis of both kinetic data and additional ¹³C-isotopic investigation, we found that the low-performance strain demonstrated robust biomass growth in the minimal growth medium (20 g/L glucose), achieving isobutanol production (up to 0.95 g/L). It utilized significant amounts of yeast extract to synthesize isobutanol when it grew in the rich medium. The rich medium also enhanced waste product secretion, and thus reduced the glucose-based isobutanol yield. In contrast, JCL260 had poor biomass growth in the minimal medium due to an inflated Monod constant (K_S), while the rich medium greatly promoted both biomass growth and isobutanol productivity (60% of the theoretical isobutanol yield). With the optimized keto-acid pathway, JCL260 synthesized isobutanol mostly from glucose even in the presence of sufficient yeast extract. This study not only provided a kinetic model for scaled-up isobutanol fermentation but also offered metabolic insights into the performance trade-off between the two engineered E. coli strains.