Optimization Of Conditions In Liquid Fermentation To Produce Nattokinase And Research About Metabolic Regulation Of Nattokinase Biosynthesis

Nattokinase(NK) is a fibrinolytic enzyme that is extracted from natto— a traditional food in Japan. Although NK was named nattokinase at first because it could cleave the fibrin clots like urokinase and streptokinase, in fact it has enzymatic property of protease. Compared with the thrombolytic agents which is being used to treat the intravascular thrombosis, NK is safer, easier to be absorbed by body because of its low molecular weight, has more direct and more persistent effect on thrombosis , and NK can be fermented by bacteria and the production cost is less. So NK is a new and potent fibrinolytic medicine.This dissertation investigated the liquid fermentation of NK. The main results were about:In the first place, a strain of bacteria, which could produce NK, was isolated from natto. It was identified to be included in the Genus Bacillus. There was a little difference between this strain and Bacillus subtilis. It may be Bacillus subtilis natto. NK produced by this strain was an extracellular enzyme.The optimized conditions in liquid fermentation were: The best nitrogen source is soya peptone. When the concentration was 3%, the bacteria had the fastest growth, but the production of NK was the most when the concentration was 2%; Xylose was the best carbon source for the yield of NK as glucose was the best for growth, 2% of xylose produced the largest number of enzyme but higher concentration of xylose suppressed the strain's growth; C: N=1 :1 was the best choice; Ca²⁺ was the positive ion which had the greatest effect on NK's synthesis, while that if Mg²⁺ was added was not very important because there were a great deal of Mg²⁺ in soya peptone; 0.02% of Ca²⁺ and Na₂HPO₄0.2%, NaH₂PO₄0.1% were the optimal conditions for NK's yield; Mn²⁺inhibited NK's biosynthesis; Surface-active agents in appropriate concentration and at appropriate time to added could increase the secretion of NK. 0.1% of sodium oleate had the best effect; The bacteria grew the fast in 40°C, but 35°C was chosen for 35°C was the most suitable for the production of NK; The strain had the biggest speed...