Changes of phytochemical constituents (isoflavones, flavanols, and phenolic acids) during cheonggukjang soybeans fermentation using potential probiotics Bacillus subtilis CS90

A potential probiotics Bacillus subtilis CS90 was isolated from Korean soybean paste (doenjang). Biotransformation of phytochemical contents, isoflavones, flavanols, and phenolic acids, during the fermentation of soybean fermented food cheonggukjang by a potential probiotics B. subtilis CS90 was investigated. The levels of isoflavone aglycones, flavanols, and gallic acid increased, while the β-glucosidase and esterase activities, isoflavone glycosides (except for acetylglycosides), and flavanol gallates contents decreased. Total isoflavone content slightly decreased after 60 h of fermentation, while total flavanol and phenolic acid content increased. The highest levels of daidzein (aglycone type) and acetyldaidzin (glycoside type) were recorded after 48 h of fermentation. However, the total contents of glycosides, manolylglycosides, and flavanol-gallates decreased by about 80, 90, and 70% during 60 h of fermenting cooked soybeans. In addition, the contents of total phenolic increased markedly from 253 mg/kg to 9414 mg/kg while the DPPH radical scavenging activity increased from 53.6 to 93.9% during this fermentation.