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SECTION II. APPLIED BIOTECHNOLOGY IN THE PHARMACEUTICAL INDUSTRY... 287nitrogen levels can inhibit synthesis. In this study, menaquinone production by strain BST2 peaked in a medium containing 20 g/L soybean peptone and declined significantly at concentrations above this threshold. Regarding the carbon source, increasing glycerol concentration from 10 g/L to 70 g/L promoted vitamin K2 production by strain BST2, yielding an increase from 505.2 %u00b5g/L to 1608.5 %u00b5g/L. Consistent with these results, Zhang et al. (2020) found that Bacillus subtilis Z-15 achieved maximum vitamin K2 production in a medium containing 3% soybean peptone and 6% crude glycerol, but levels decreased when nitrogen and carbon sources were further increased to 5% and 10%, respectively [10].In a medium optimized with 70 g/L glycerol, 20 g/L soybean peptone, and 0.5 g/L K2HPO4, Bacillus subtilis BST2 produced a maximum yield of 2694.5 %u00b5g/L of vitamin K2 after 120 hours of fermentation. This yield is slightly lower than the 3.593 mg/L of menaquinone synthesized by Bacillus subtilis natto, which was mutated to enhance menaquinone production as reported by Song et al. (2014), but significantly higher than the 0.3158 mg/L of menaquinone produced by Bacillus subtilis natto IBRC-M 11153 in the study by Sharifzadeh et al. (2022). Thus, Bacillus subtilis BST2 has the potential for application in fermented foods to provide a natural source of vitamin K2 supplementation in the human diet.5. CONCLUSIONSAmong the 14 Bacillus subtilis strains analyzed, BST2 exhibited the highest capacity for vitamin K2 production, with a yield of 1170.5 %u00b5g/g of freeze-dried cells. The optimal nutrient conditions for vitamin K2 synthesis by strain BST2 were determined to be 70 g/L glycerol, 20 g/L soybean peptone, and 0.5 g/L K2HPO4. Under these conditions, strain BST2 produced a maximum menaquinone concentration of 2694.5 %u00b5g/L after 120 hours of fermentation.