optimization of culture condition for the production of menaquinone-7 by bacillus subtilis natto

Background: vitamin k2 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 k2 is menaquinone-7 (mk-7), an expensive raw material with no local manufacturers in iran. objectives: since there was no report on the yield of mk-7 produced by the currently available bacillus subtilis natto species in iran, this study aims to optimize the culture condition for the production of mk-7 using this bacillus species. materials and methods: the base medium (bm) for mk-7 production contained glycerol (6.3%), soybean peptone (3%), and yeast extract (0.51%). the selected factors for optimizing the mk-7 production included the incubation temperature (30, 37, and 40°c) and incubation time (72, 96, and 120hr) with/without the addition of k2hpo4 to the fermentation medium. three sets of experiments with six modes in each set were designed based on these parameters. mk-7 content was analyzed by the hplc method. results: two experiments showed the highest mk-7 production yields of 0.319 and 0.3158 mg/l. the culture condition for both of these yields was as follows:120 hours incubation time in the presence of k2hpo4. however, the incubation temperature was different in these two experiments. the incubation temperature of 30°c resulted in 0.319 mg/l mk-7 concentration, and 37°c yielded 0.3158 mg/l. conclusion: b. subtilis natto (ibrc-m 11153) 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-7 to lower the cost of microbial production and make the industrial process economic.