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Metabolic engineering of Corynebacterium glutamicum for L-cysteine production

Wei, Liang, Wang, Hao, Xu, Ning, Zhou, Wei, Ju, Jiansong, Liu, Jun, Ma, Yanhe
Applied microbiology and biotechnology 2019 v.103 no.3 pp. 1325-1338
Corynebacterium glutamicum, biosynthesis, cysteine, metabolic engineering, pharmaceutical industry, serine, serine O-acetyltransferase, sulfur, thiosulfates, toxicity, transporters
L-cysteine, a valuable sulfur-containing amino acid, has been widely used in food, agriculture, and pharmaceutical industries. Due to the toxicity and complex regulation of L-cysteine, no efficient cell factory has yet been achieved for L-cysteine industrial production. In this study, the food-grade microorganism Corynebacterium glutamicum was engineered for L-cysteine production. Through deletion of the L-cysteine desulfhydrases (CD) and overexpression of the native serine acetyltransferase (CysE), the initial L-cysteine-producing strain CYS-2 was constructed to produce 58.2 ± 5.1 mg/L of L-cysteine. Subsequently, several metabolic engineering strategies were performed to further promote L-cysteine biosynthesis, including using strong promoter tac-M to enhance expression intensity of CysE, investigating the best candidate among several heterogeneous feedback-insensitive CysEs for L-cysteine biosynthesis, overexpressing L-cysteine synthase (CysK) to drive more metabolic flux, evaluating the efflux capacity of several heterogeneous L-cysteine transporters, engineering L-serine biosynthesis module to increase the precursor L-serine level and using thiosulfate as the sulfur source. Finally, the L-cysteine concentration of the engineered strain CYS-19 could produce 947.9 ± 46.5 mg/L with addition of 6 g/L Na₂S₂O₃, approximately 14.1-fold higher than that of the initial strain CYS-2, which was the highest titer of L-cysteine ever reported in C. glutamicum. These results indicated that C. glutamicum was a promising platform for L-cysteine production.