Effects of Chromosomal Integration of the Vitreoscilla Hemoglobin Gene (vgb) and S-Adenosylmethionine Synthetase Gene (metK) on ε-Poly-L-Lysine Synthesis in Streptomyces albulus NK660.

ε-Poly-L-lysine (ε-PL) is a widely used natural food preservative. To test the effects of the Vitreoscilla hemoglobin (VHb) and S-adenosylmethionine (SAM) on ε-PL synthesis in Streptomyces albulus NK660, the heterologous VHb gene (vgb) and SAM synthetase gene (metK) were inserted into the S. albulus NK660 chromosome under the control of the constitutive ermE* promoter. CO-difference spectrum analysis showed S. albulus NK660-VHb strain could express functional VHb. S. albulus NK660-VHb produced 26.67 % higher ε-PL and 14.57 % higher biomass than the wild-type control, respectively. Reversed-phase high-pressure liquid chromatography (RP-HPLC) results showed the overexpression of the metK gene resulted in increased intracellular SAM synthesis in S. albulus NK660-SAM, which caused increases of biomass as well as the transcription level of ε-PL synthetase gene (pls). Results indicated that the expression of vgb and metK gene improved on ε-PL synthesis and biomass for S. albulus NK660, respectively.