Diversity of Bacillus groups isolated from fermented soybean foods ('Doenjang' and 'Kanjang') and their fermentation characteristics of 'Cheonggukjang'

Abstract

In this study, Bacillus strains were isolated from Korean traditional fermented foods, 'Doenjang' and 'Kanjang', and the fermentative properties of 'Cheonggukjang' prepared using these strains were analyzed. During the fermentation of 'Chenoggukjang', viable cell count, average ß-glycosidase activity, and ammonia level were calculated as 9.49-13.13 log CFU/mL, 22.15 unit/g, and 77.52-273.63 mg/100 g, respectively. γ-aminobutyric acid (GABA) content was highest when using B. subtilis MGD07 (81.33 mg/100 g), whereas it was lowest when using B. cytotoxicus MGD01 (12.56 mg/100 g). Moreover, the presence of ß-glycoside forms such as daidzin and genistin, decreased during fermentation, which corresponed to the increase in aglycone forms including daidzein and genistein, observed after fermentation. Additionally, the content of daidzein (249.78 μg/g), glycitein (39.23 μg/g), and genistein (23.61 μg/g) was highest in 'Cheonggukjang' prepared using B. licheniformis MGD05 isolated from 'Doenjang'. Conversely, the total aglycone content was highest (305.55 μg/g) in 'Cheonggukjang' prepared using B. subtilis MGK04 isolated from 'Kanjang'. In addition, the total polyphenol content and antioxidant activity, such as DPPH and ABTS radical scavenging, were higher in all 'Cheonggukjang' extracts than in steamed soybeans. In particular, B. amyloliquefaciens MGD02 and B. subtilis MGK02 produced low levels of ammonia and exhibited enhanced functional components (GABA and non-glycoside isoflavones). Copyright ? The Korean Society of Food Preservation.