LAUSR

Cysteine synthase A (CysK) catalyzes the last reaction of l‐cysteine synthesis in bacteria, but its moonlighting functions have been revealed recently. In this study, CysK was overexpressed in Corynebacterium glutamicum IWJ001, an l‐isoleucine producer. Compared with the control IWJ001/pDXW‐8, IWJ001/pDXW‐8‐cysK cells grew fast during log phase, and produced 26.5% more l‐isoleucine in flask fermentation and 23.5% more l‐isoleucine in fed‐batch fermentation. The key genes aspC, lysC, hom, thrB, ilvA, and ilvBN involved in l‐isoleucine biosynthesis were all upregulated in IWJ001/pDXW‐8‐cysK, compared with IWJ001/pDXW‐8. In addition, IWJ001/pDXW‐8‐cysK cells were longer and thicker than IWJ001/pDXW‐8 cells. Compared with IWJ001/pDXW‐8, the membrane permeability increased 15.8% and biofilm formation ability decreased 71.3% for IWJ001/pDXW‐8‐cysK cells. The results demonstrate that CysK overexpression in C. glutamicum is a good approach to enhance l‐isoleucine production.