Vitamin K2 (Menaquinone-7) production by Bacillus subtilis natto by using a glucose-based medium in biofilm reactors

摘要

Menaquinone-7 (MK-7) is a subtype of vitamin K which plays a key role in promoting heart and bone health. MK-7 can be excreted by many strains of bacteria. Among these strains, Bacillus subtilis natto seems to hold a key position. On the other hand, Bacillus subtilis, especially in static fermentations, tends to form pellicles and possibly biofilms under suitable conditions which promote MK-7 secretion but at the same time create operational and scaling up issues during fermentation. Therefore, biofilm reactors seem to be a viable strategy to create a controlled environment for the bacteria to form biofilm and simultaneously address operational and scaling up issues through robust agitation and aeration. The present study aims at using a suitable Plastic Composite Support (PCS) and Bacillus strain to optimize the media components and growth conditions in a glucose-based medium using a biofilm reactor. The optimum conditions were found as 30°C, 234 rpm and pH 6.48, and the optimum composition was of glucose (152.6 g/L), yeast extract (8 g/L) and casein (17.6 g/L) yielding a maximum MK-7 concentration of 20.46±0.51 mg/L in batch biofilm reactors Furthermore, MK-7 concentrations were enhanced using a fed-batch strategy to concentrations as high as28.7±1.1 mg/L, which was 40.3% higher as compared to the batch process.