Rational modification of the carbon metabolism ofCorynebacterium glutamicumto enhancel-leucine production

摘要

l-Leucine is an essential amino acid that has wide and expanding applications in the industry. It is currently fast-growing market demand that provides a powerful impetus to further increase its bioconversion productivity and production stability. In this study, we rationally engineered the metabolic flux from pyruvate tol-leucine synthesis inCorynebacterium glutamicumto enhance both pyruvate availability andl-leucine synthesis. First, thepyc(encoding pyruvate carboxylase) andavtA(encoding alanine-valine aminotransferase) genes were deleted to weaken the metabolic flux of the tricarboxylic acid cycle and reduce the competitive consumption of pyruvate. Next, the transcriptional level of thealaTgene (encoding alanine aminotransferase) was down regulated by inserting a terminator to balancel-leucine production and cell growth. Subsequently, the genes involved inl-leucine biosynthesis were overexpressed by replacing the native promoters P(leuA)and P(ilvBNC)of theleuAgene andilvBNCoperon, respectively, with the promoter P(tuf)ofeftu(encoding elongation factor Tu) and using a shuttle expression vector. The resulting strain WL-14 produced 28.47 +/- 0.36 g/Ll-leucine in shake flask fermentation.