Isolation and Sensory Evaluation of High Nattokinase-Producing Strains from Guizhou Douche, A Traditional Chinese Fermented Soybean

Authors: Wu J, Li C and He L*

DOI: 10.23880/ijbp-16000206

Volume 7, Issue 1

Abstract

Nattokinase (NK) has become the focus of recent research on thrombolytic products. The preliminary screening got 361 strains with hydrolyzed circles in casein plates from douche, a traditional fermented soybeans by native microorganisms. Then, NKproducing isolates 5 and 7 with high NK activity and excellent sensory score in fermented soybean were further screened from the 361 strains through casein hydrolysis cycle area and fibrin plate methods and sensory evaluation of solid-state fermentation with principal component analysis. The NK activity of the two strains was around 6000 IU g-1. The fermented soybean by the two strains was yellow in color, moist in texture, unique in taste, and rich in mucus and sticky silk, which indicated the excellent performance of the two strains. Through morphological, physiological and 16S rDNA analysis, isolates 5 and 7 were identified as Bacillus amyloliquefaciens and Bacillus subtilis, respectively. This study laid a foundation for the potential application of the two strains in the modern fermentation control of traditional Guizhou fermented soybean and the production of NK products.

Keywords: Bacillus amyloliquefaciens Isolate 5; Bacillus subtilis Isolate 7; Nattokinase; Screening; Sensory Evaluation; Principal Component Analysis

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