Abstract:In order to improve the yield and diversity of vitamin K2 produced by microbial fermentation，the fermentation conditions of Bacillus subtilis DC?1 were optimized.The fermentation conditions including carbon source，nitrogen source，and inorganic salt were optimized by single factor experiment.The factors that had a significant influence on vitamin K2 produced by DC?1 were screened by the Plackett?Burman（PB）experi?ment，and the optimal fermentation conditions of DC?1 were obtained by response surface Box?Behnken de?sign.The results showed that the optimal fermentation conditions for vitamin K2 produced by DC?1 were glyc?erol of 36.5 g/L，molasses of 31.8 g/L，soybean flour of 32.5 g/L，KH2PO4 of 0.3 g/100 mL，K2HPO4·3H2O of 0.8 g/100 mL，MgSO4·7H2O of 0.7 g/100 mL，and NaCl of 0.5 g/100 mL.Under these conditions，the yield of MK?7 reached 94.66 mg/L，which was 48.04% higher than the initial fermentation conditions.Meanwhile，the diversity of vitamin K2 produced by strain DC?1 increased，and a liquid chromatograph mass spectrometer（LC?MS）identified that it could produce five MK homologues simultaneously，namely MK?2，MK?3，MK?4，and MK?7，of which one analogue could not be found in the high?resolution mass spectrometry and was presumed to be MK?5 or MK?6 based on the retention time.This could lay a foundation for the industrial production of vi?tamin K2 and the exploration of the biological activity of vitamin K2 homologues.