Quantitative analyses for several nutrients and volatile components during fermentation of soybean by Bacillus subtilis natto

This study is to reveal the variation of five pivotal substances, including polysaccharides, proteins, isoflavones, fatty acids and volatile components during the soybean fermentation process by Bacillus subtilis natto. After 96 h of soybean fermentation, the polysaccharide contents were significantly decreased, and the glucose and galactose contents showed the greatest decline in all the monosaccharide components. Moreover, isoflavone glycoside levels were decreased, while the isoflavone aglycone levels were increased following the fermentation. In addition, the SCFAs contents were also significantly increased in comparison with the unfermented soybean. Furthermore, 16 amino acids and 36 volatile components were detected in the fermented soybean. Finally, 21 key compounds were identified through PCA and OPLS-DA analysis of total compounds in the fermentation process. These findings demonstrated that Bacillus subtilis natto had a significant influence on the biochemical profiles of soybean fermentation and consequently contributed to its unique quality.