Optimization of Culture Condition for the Production of Menaquinone-۷ by Bacillus Subtilis Natto

Background: Vitamin K۲ refers to a series of naphthoquinone derivatives, which have a variety of physiological and pharmacological functions for the human body. The most important type of vitamin K۲ is menaquinone-۷ (MK-۷), an expensive raw material with no local manufacturers in Iran. Objectives: Since there was no report on the yield of MK-۷ produced by the currently available Bacillus subtilis natto species in Iran, this study aims to optimize the culture condition for the production of MK-۷ using this Bacillus species. Materials and Methods: The base medium (BM) for MK-۷ production contained glycerol (۶.۳%), soybean peptone (۳%), and yeast extract (۰.۵۱%). The selected factors for optimizing the MK-۷ production included the incubation temperature (۳۰, ۳۷, and ۴۰°C) and incubation time (۷۲, ۹۶, and ۱۲۰hr) with/without the addition of K۲HPO۴ to the fermentation medium. Three sets of experiments with six modes in each set were designed based on these parameters. MK-۷ content was analyzed by the HPLC method. Results: Two experiments showed the highest MK-۷ production yields of ۰.۳۱۹ and ۰.۳۱۵۸ mg/L. The culture condition for both of these yields was as follows:۱۲۰ hours incubation time in the presence of K۲HPO۴. However, the incubation temperature was different in these two experiments. The incubation temperature of ۳۰°C resulted in ۰.۳۱۹ mg/L MK-۷ concentration, and ۳۷°C yielded ۰.۳۱۵۸ mg/L. Conclusion: B. subtilis natto (IBRC-M ۱۱۱۵۳) is suitable to be used as a basic platform for the mutation and production of a high-producer species. Optimizing the culture conditions using the wild-type species is not beneficial in increasing the production ability of the bacterium. It is necessary to use different methods for enhancing the production yield of MK-۷ to lower the cost of microbial production and make the industrial process economic.

Keywords:

Vitamin K۲ , Bacillus subtilis natto , Menaquinone-۷ , fermentation