Abstract:[Background] Enzymatic transformation for production of D-mannose has attracted considerable attention. [Objective] The production conditions of D-mannose were investigated using the co-expressed E. coli cells harboring D-glucose isomerase (D-GIase) and D-lyxose isomerase (D-LIase). [Methods] The synthesized D-GIase and D-LIase gene fragments were digested and ligated into the vector pCDFDuet-1. Then, the resultant recombinant plasmid pCDFDuet-Acce-DGI/Peba-DLI was transformated into E. coli BL21(DE3) strain to co-express the two enzymes. After collecting the cells co-expressing D-GIase and D-LIase by shake flask culture, the reaction conditions of the co-expression cells were determined. [Results] The optimal temperature and pH of enzymes in the co-expressing system were 70 °C and 6.0 in the presence of Co2+ (1 mmol/L), respectively. After the reaction reached equilibrium, 13.8, 38.1 and 62.6 g/L of D-mannose were obtained from 100, 300 and 500 g/L of D-glucose, which corresponded to a conversion of 13.8%, 12.7% and 12.5%, respectively, and the equilibrium ratio of D-glucose, D-fructose and D-mannose was about 50?37.5?12.5. [Conclusion] A co-expression system consisted of D-GIase and D-LIase in E. coli cells can be used for one-pot production of D-mannose from D-glucose.
