Nattokinase’s extraction from Bacillus subtilis fermented soybean curd residue and wet corn distillers’ grain and fibrinolytic activities

摘要

To recycle and reuse food wastes , soybean curd residue (SCR) and wet corn distillers’ grain (WDG) were used as substrate s in Bacillus subtilis fermentation to extract nattokinase (NK). The extract conditions of Natto - NK , as well as the f ibrinolytic activity of SCR -NK , WDG -NK and Natto - NK were investigated. It was showed that the highest Natto - NK yield could reach 0.108 g per 150 g Natto (wet), when extract conditions were involved with saline ( 0.9% ) 375 ml, (NH 4 ) 2 SO 4 30 g and the ratio of 3/4 between ethanol and saline . After f ibri n h ydrolysis for 4 h , both hydrolyzed areas of SCR -NK and WDG -NK were 49 mm 2 in one hole, consistent with that of Natto - NK . Apart from this, as a result calculated according to the dried substrate, the SCR-NK yields (0.415 g/150 g) were significantly higher than Natto-NK yields (0.270 g/150 g). Moreover, SCR-NK (1.3 fibrinolytic unit/ml ( FU/ml)) showed superior activity compared with that of Natto - NK , although there was no statistics difference. Our results suggested that SCR could be regarded as a promising fermentation source for NK production.