PB0195 - Bacillus subtilis fermentation by soybeans ―Natto and Yunnan (SL-001)―

Background: We previously reported the isolation of the fibrinolytic enzyme nattokinase from natto, produced by Bacillus subtilis, featuring a single-stranded polypeptide structure with a molecular weight of approximately 27,700.

Aims: In this study, we discovered that the Yunnan SL-001 fermentation product exhibits distinct substrate specificity from natto, demonstrating potent α-glucosidase inhibitory activity.

Methods: The fermentation product was prepared by fermenting at 37℃ for 24 hours using conventional methods. The fibrin plate method, amidase substrate method, and the analysis of dipicolinic acid and vitamin K₂ were all conducted as previously reported.

Results: SL-001, deposited internationally under commission number FERMBP-6713 at the Industrial Technology Research Institute of the Ministry of International Trade and Industry, belongs to the Bacillus subtilis genus. It displayed a stronger effect on substrateⅡ(Suc-Ala-Ala-Pro-Phe-pNA) compared to substrateⅠ(Bz-Ile-Glu-(OR)-Gly-Arg-pNA) when fermented with soybeans (Yunnan strain SubⅠ/SubⅡ=approximately 0.62). The fibrinolytic activity was around 500mm²/30µl (37℃, 24hours). This fermentation product contained a high amount of dipicolinic acid (27mg/g) and vitamin K₂ (9.071µg/g).
In contrast, a type of natto bacteria, Naruse strain SubⅠ/SubⅡ=approximately 2.00, exhibited nattokinase activity (fibrinolytic activity) of approximately 600mm²/30µl (37℃, 24hours). The α-glucosidase inhibitory activity of the Yunnan strain fermentation product was found to be a low molecular weight compound (molecular weight less than 10,000) that adsorbs to Sephacryl gel and is heat-resistant at 100℃.
The Yunnan strain fermentation product appeared to be less sticky compared to natto.

Conclusion(s): The Yunnan strain belongs to the same Bacillus subtilis genus as natto bacteria, and its fermentation product is similar to natto. However, it was found that only the Yunnan strain produces an α-glucosidase inhibitory substance related to anti-diabetic properties.