Development of a two-stage feeding strategy based on the kind and level of feeding nutrients for improving fed-batch production of l-threonine by Escherichia coli----中国科学院微生物研究所

科研成果

论文题目:	Development of a two-stage feeding strategy based on the kind and level of feeding nutrients for improving fed-batch production of l-threonine by Escherichia coli
作者:	Liu Shuwen, Liang Yong, Liu Qian, Tao Tongtong, Lai Shujuan, Chen Ning, Wen Tingyi
联系作者:	Wen Tingyi
刊物名称:	Applied Microbiology and Biotechnology
期:	2
卷:	97
页:	573-583
年份:	2013
影响因子:	3.613
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摘要:	Fed-batch fermentation is the predominant method for industrial production of amino acids. In this study, we comprehensively investigated the effects of four kinds of feeding nutrients and developed an accurate optimization strategy for fed-batch production of l-threonine. The production of l-threonine was severely inhibited when cell growth ceased in the bath culture. Similarly, l-threonine production was also associated with cell growth in the carbon-, phosphate-, and sulfate-limited fed-batch cultures, but the accumulation of l-threonine was markedly increased because of the extended production time in the growth stage. Interestingly, auxotrophic amino acid (l-isoleucine)-limited feeding promoted l-threonine production over the non-growth phase. Metabolite analysis indicates that substantial production of acetate and glutamate and the resulting accumulation of ammonium may lead to the inhibition of l-threonine production. During the growth phase, the levels of l-isoleucine were accurately optimized by balancing cell growth and production with Pontryagin's maximum principle, basing on the relationship between the specific growth rate mu and specific production rate rho. Furthermore, the depletion of l-isoleucine and phosphate at the end of the growth phase favored the synthesis of l-threonine in the subsequent non-growth phase. Combining the two-stage feeding profiles, the final l-threonine concentration and conversion rate were increased by 5.9- and 2.1-fold, respectively, compared to batch processes without feeding control. The identification of efficient feeding nutrient and the development of accurate feeding strategies provide potential guidelines for microbial production of amino acids.