Screening for Optimal Parameters of Nattokinase Synthesis by Bacillus subtilis natto in Solid-State Fermentation

Abstract

Nattokinase, which is an extracellular enzyme synthesized by Bacillus subtilis natto, is a medication for cardiovascular disease treatment. In this study, soybean seed was used as a substrate for culturing Bacillus subtilis natto in solid-state fermentation to produce nattokinase. The optimal culture parameters for solid-state fermentation to synthesize nattokinase by Bacillus subtilis natto were 2:50 (v:w) of the ratio of Bacillus subtilis natto pre-culture to the substrate, 42 h of fermentation time, and 3 cm of the thickness of the substrate. At this optimal culture parameter of solid-state fermentation by using Bacillus subtilis natto, the enzymatic activity of crude nattokinase was 7.13 ± 0.2, 16.24 ± 0.33, and 16.55 ± 0.06 (specific activity/mL), respectively. Furthermore, we aim to apply this study with large scale production initially. Thus, the ratio of reusing Bacillus subtilis natto in fermentation product to substrate for a new process of solid-state fermentation and circulation time of reusing Bacillus subtilis natto in new solid fermentation process were screened. The maximal enzymatic activity of crude nattokinase of 14.10 ± 0.18 (specific activity/mL) was found at 3:100 (w:w) of reusing Bacillus subtilis natto in fermentation product to substrate for a new process of solid-state fermentation. The suggestion for the circulation time of reusing Bacillus subtilis natto for new solid fermentation process was 2nd. The results of this study had provided the necessary information for further research on nattokinase.