Co-Expression of Threonine Dehydratase and Acetolactate Synthase in Escherichia Coli for L-Isoleucine Production

Abstract

Metabolic engineering ofCorynebacterium glutamicumhas sought to divert carbon into L-isoleucine. However, the fermentation period of this strain is long. TheC.glutamicumYILW strain (LeuL, AHVr, SGr, Leu-MEr) was previously derived by repeated compound mutagenesis which could accumulate 20.2 g/L L-isoleucine in a 5-L jar fermentor. Overexpression of the threonine dehydratase gene (ilvA) fromCorynebacterium glutamicumYILW and coexpression of threonine dehydratase and acetolactate synthase (ilvBN) from it were employed to divert carbon flux toward L-isoleucine. The strainE. coliTRFC with the expression ofilvA could accumulate L-isoleucine of 6.8 g/L without accumulation of any L-threonine by fed-batch fermentation in a 5-L jar fermentor. However, the production of L-isoleucine by the strainE.coliTRFC with the co-expression ofilvA andilvBN was decreased by 19.1%, and the production of L-valine was increased by 40% compared with that ofE. coliTRFC with the expression ofilvA.