Abstract
To recycle and reuse food wastes, soybean curd residue (SCR) and wet corn distillers’ grain (WDG) were used as substrates in Bacillus subtilis fermentation to extract nattokinase (NK). The extract conditions of Natto-NK, as well as the fibrinolytic 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, (NH4)2SO4 30 g and the ratio of 3/4 between ethanol and saline. After fibrin hydrolysis for 4 h, both hydrolyzed areas of SCR-NK and WDG-NK were 49 mm2 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.
Highlights
NK is primarily found from a traditional fermented soybean food named as “Natto” in Japan (Sumi, et al, 1987)
In a rat mode, Fujita et al (1995a) demonstrated that NK absorbed from the intestinal tract can cleave fibrinogen in plasma after intraduodenal administration of the enzyme, and the thrombolytic activity of NK is stronger than that of plasmin (Fujita, et al, 1995b; Fujita, et al, 1995)
Natto-NK, soybean curd residue (SCR)-NK, and wet corn distillers’ grain (WDG)-NK were measured, and fibrinolytic efficiency was expressed as the average area of those holes in one fibrin plate
Summary
NK is primarily found from a traditional fermented soybean food named as “Natto” in Japan (Sumi, et al, 1987). SCR can be fermented by cellulolytic Aspergillus (Khare, et al, 1995), Bacillus subtilis (Ohno, et al, 1995; Zhu, et al, 2008) and Ganoderma lucidum (Hsieh & Yang, 2004) to produce citric acid, antioxidant, iturin A or fruit body of G. lucidum. Those utilizations, expected to reduce both environment load and production costs of high-value materials, are important in microbial fermentation for production of industrial enzymes, such as Nattokinase (NK). The fibrinolytic activities of SCR-NK, WDG-NK and Natto-NK were well compared and evaluated
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