Characterization of soybean fermented by aflatoxin non-producing Aspergillus oryzae and γ-aminobutyric acid producing Lactobacillus brevis

Abstract

Fermented soybean products may contain aflatoxins due to the contamination of the aflatoxin producing mold during natural fermentation or as a result of un-prudential use of starter strain. The aim of the present study was to develop and characterize fermented soybean products with enhanced safety and bioactive compound using aflatoxin non-producing Aspergillus oryzae FMB S46471 and γ-aminobutyric acid (GABA) producing Lactobacillus brevis GABA 100. For fermentation, steam-processed soybeans were inoculated with A. oryzae FMB S46471. The scaled-up fermentation product was fermented for 17 days, including 12 days fermentation with A. oryzae and 5 days with L. brevis, and contained 6.5±0.3 g/kg of GABA and 45.7±0.3 g/kg of total free amino acids. After ripening for 90 days, the fermented soybean contained about 11.6±0.3 g/kg of GABA and 72.7±1.8 g/kg of total free amino acids. Furthermore, aflatoxins were not detected in both mature and immature soybean products. The soybean product that fermented by an aflatoxin non-producer and a powerful GABA producer will contribute to the development of fermented foods with enhanced safety levels and functional benefits of GABA.