Development of Doenjang Enriched with GABA and Aglycone Isoflavones by Mixed Fermentation of Aspergillus oryzae and Lactobacillus brevis

Abstract

A new fermentation process for doenjang with increased GABA and aglycone isoflavones content was developed by a mixed culture of Lactobacillus brevis and Aspergillus oryzaeas starters. Lactobacillus brevis GABA 100 (2.5 mL 1010 cfu/mL) and Aspergillus oryzae FMB S40250 (5 mL 108 cells/mL) were co-inoculated into the enzyme-treated soybean medium and cultured for 24 h to produce starter for doenjang fermentation. Then, the starter was mixed with steamed soybean for doenjang fermentation. Content of GABA and isoflavones were determined by TLC and HPLC. The doenjang at its seventh fermentation day contained 7162 μg/g GABA, 60 μg/g daidzein and 59 μg/g genistein, which were higher or comparable to traditional doenjang fermented more than one year. The results showed that the contents of GABA and aglycone isoflavones in the doenjang were enriched by co-cultivation of L. brevis GABA 100 and A. oryzae FMB S40250.