Process optimization of co-fermentation natto with Lactobacillus bulgaricus and characteristic analysis

Natto is a functional food, but it produces an unpleasant smell during the fermentation process. To eliminate the unacceptable smell, Lactobacillus bulgaricus and Bacillus subtilis were used to co-ferment soybeans in this study. The optimal conditions of co-fermentation anaerobic fermentation were: fermentation time 20 h, temperature 35 °C, strain ratio 1:1, and inoculum amount 4%. After optimization, fibrinolytic activity, antioxidant activity, polyphenol content, and γ-polyglutamic acid (γ-PGA) yield of Natto were increased by 15.2%, 10.9%, 29.1%, and 72.3%. It also introduced a wealth of probiotics with lactic acid bacteria up to 1.45 X 10¹⁰cfu/g. The co-fermented natto had unique fruity and lactic flavor, and high sensory score based on the flavor and sensory analysis. The activity and value of natto have been increased through co-fermentation, making it possible to improve natto.