Enhanced vitamin K (Menaquinone-7) production by Bacillus subtilis natto in biofilm reactors by optimization of glucose-based medium

Background: Benefits of vitamin K have been reported by many studies recently, due to its ability to reduce the risk of cardiovascular diseases and its potential benefits against osteoporosis. Specifically, menaquinone-7 (MK-7), being the most potent form of vitamin K, has definitely received most of the attention. Currently, solid or static liquid fermentation strategies are utilized for industrial production of MK-7 by Bacillus strains. However, these strategies face fundamental operational and scale-up issues as well as intense pellicle and biofilm formations which is problematic in static liquid fermentation, due to heat and mass transfer inefficiencies they create. Objective: The purpose of this study was to demonstrate that biofilm reactors will overcome the issues associated with suspended cell reactors when using Bacillus strains to produce MK-7. The expectation is that the use of biofilm reactors will result in a significant increase in the production of MK-7. Method: Vitamin K production by Bacillus subtilis natto when grown in a biofilm reactor was evaluated at various concentrations of the three major nutrients, glucose, yeast extract and casein. The data was analyzed using response surface methodology (RSM). Results: The maximum concentration of MK-7 in the biofilm reactors was 20.5±0.5 mg/L, which was a 344 % increase when compared to the amount produced in suspended-cell reactors containing the same optimum media composition. Conclusion: These results demonstrate the potential of utilizing biofilm reactors for MK-7 production on an industrial scale.