The production of enantiopure d-lysine from l-lysine by a two-strain coupled system

Abstract

Abstract The microbial production of d -lysine to replace chemical approach has gained great interest with the rising concerns over the environment. Here, we employed recombinant E. coli strain BL21-LYR with lysine racemase and strain BL-22A-RB-YB with l -lysine monooxygenase and 5-aminovaleramide amidohydrolase to establish a two-strain coupling whole-cell bioconversion system for d -lysine production from l -lysine. To improve the optical purity of d -lysine, the optimal reaction condition for resolution of dl -lysine after the racemization was investigated. The specificity of BL-22A-RB-YB for l -lysine and the effects of reaction condition on bioconversion efficiency of whole-cell were accordingly determined. Under the optimal condition, a maximum 53.5 g·L−1 d -lysine and 48.2 g·L−1 5-AVA were obtained with yield of 47.4% and 42.3%, respectively, by the microbial racemization and asymmetric degradation process. The final d -lysine enantiomeric excess was over 99%. Meanwhile, a valuable compound 5-aminovaleric acid was synthesized with the production of d -lysine, indicating the economic feasibility of the two-strain coupling system.