MK-7 production was closely coupled with cell growth.As can be concluded from Fig. 3, MK-7 concentration increased approximately 3-fold between cell's mid-exponential growth and the stationary phase,reaching its optimal concentration after 48 h(11.2270.6 mg/L).According to the results glycerol concentration in the medium stridently decreased to approximately 0.2% at the end of the fermentation;coinciding with an increase in biomass and MK-7 production.Our results show that the great bulk of MK-7 was mainly produced at the stationary phase where the concentration of glycerol as a carbon source was limited.pH of the media decreased from 6.65 to 5.32 after the cell growth rate reached its maximum level after 30 h.