Increasing the Production of Nattokinase and Vitamin K2 in Natto with Dipicolinic Acid

It was found that when dipicolinic acid is added to the culture solution of Bacillus subtilis natto, the area of fibrin dissolved by nattokinase (standard fibrin plate) and the amidase activity of nattokinase against Suc- Ala-Ala-Pro-PhepNA increased. For example, when manufacturing natto using steamed soybeans, the addition of 10-64 mM of dipicolinic acid increases amidase activity by more than 10 times. The concentration of vitamin K2 (menaquinone-7) also increased by about 4 times with the addition of 10 mM of dipicolinic acid. No other food contains such a high concentration of vitamin K2. The results were the same for the shaking culture as well as for the stationary culture. If the concentration of dipicolinic acid is appropriately controlled, a product with excellent levels for both nattokinase activity and vitamin K2 concentration could be manufactured.