Screening and Optimizing Fermentation Conditions of Bacillus Strain with High Productive Vitamin K₂

In order to obtain high-yield strain of synthesizing vitamin K₂(MK-7),strains were screened from the soil riched in Bacillus,and was identified by sequence alignment of 16S rRNA and the gyrB sequence amplified and blast by PCR. The phylogenetic trees was constructed and MK-7 from fermentation products of the stain was extracted and analyzed. Carbon,nitrogen and inorganic salts in the fermentation medium was also optimized. It was found that the microorganism belonged to the genus Bacillus amyloliquefaciens and most of synthesis MK-7 was secreted extracellularly. Glycerol was the best carbon source for MK-7 synthesis,and the optimum concentration was 5%. Soy peptone was the best nitrogen source,and the optimum concentration was 12%. Proper concentration of phosphate and metal ions(Ca²⁺ and Mg²⁺)could promote the synthesis of MK-7.The optimum concentration of inorganic salts for synthesis of MK-7 were 0.7 g/L(K₂HPO₄),0.2 g/L(CaCl₂·2H₂O)and 0.5 g/L(MgSO₄·7H₂O). By using the optimized medium,and the yield of MK-7 synthesized by the strain reached 70 mg/L or more.