期刊
APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY
卷 171, 期 1, 页码 20-30出版社
SPRINGER
DOI: 10.1007/s12010-013-0321-0
关键词
Corynebacterium glutamicum; L-isoleucine; thrABC overexpression; alaT deletion; By-products
资金
- National High Technology Research and Development Program [2012AA02A703, 2012AA022102, 2013AA102106]
- Tianjin Municipal Science and Technology Commission [12ZCZDSY01900, 12ZXCXSY05900]
- Tianjin Municipal Education Commission [20120630]
- Program for Changjiang Scholars and Innovative Research Team in University [IRT 1166]
l-isoleucine is synthesized from 2-ketobutyrate and pyruvate in Corynebacterium glutamicum, and the supplies of these two precursors are important for l-isoleucine synthesis. C. glutamicum YILW Delta alaT with alaT gene deletion (encoding alanine aminotransferase, a principal enzyme for l-alanine synthesis) was constructed to increase intracellular pyruvate availability, and the thrABC genes from Escherichia coli (encoding bifunctional aspartate kinase I-homoserine dehydrogenase I, homoserine kinase, and threonine synthetase) were overexpressed in C. glutamicum YILW and YILW Delta alaT to increase the supply of intracellular 2-ketobutyrate. In the fed-batch fermentation, YILWpXMJ19thrABC, YILW Delta alaT, and YILW Delta alaTpXMJ19thrABC exhibited 5.3, 17.6, and 8.4 % higher l-isoleucine production than the original strain, respectively. Both YILWpXMJ19thrABC and YILW Delta alaT excreted lower concentrations of l-lysine, l-alanine, and l-valine. YILW Delta alaTpXMJ19thrABC exhibited a cumulative reduction of these by-products excretion, which indicated that thrABC overexpression combined with alaT deletion resulted in the metabolic flux redistribution from 2-ketobutyrate and pyruvate to l-isoleucine synthesis, and decreased the fluxes to by-products synthesis accordingly.
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