Effect of media components and morphology of Bacillus natto on menaquinone-7 synthesis in submerged fermentation

Vitamin K₂ (menaquinone or MK) plays an important role in blood clotting, cardiovascular disease, and anti-osteoporosis. A novel bacterial strain was isolated and identified as Bacillus natto based on 16SrDNA sequencing and LC-MS analysis. The objective of this study was to improve the extraction efficiency and productivity of MK-7 from B. natto. Acid-heating method efficiently disrupted B. natto cells for MK-7 extraction. Bacillus natto had a wide range of pH (5.0 ~ 9.0) for optimal growth. Its MK-7 yield was increased when rotation speed was increased to 200 rpm. The highest MK-7 yield was obtained when glycerol and soy peptone were used in the growth media. Batch fermentation was subsequently tested in 5 L bioreactor, which gave a high productivity of MK-7 (at 0.60 mg/L/h). A positive correlation between MK-7 yield and sporulation ratio was also found. This study provides valuable information on the extraction and production of menaquinone-7 from B. natto under submerged fermentation condition.