Production of a novel lycopene-rich soybean food by fermentation with Bacillus amyloliquefaciens

Fermented soybean is abundant in nutrients and bioactive ingredients. Lycopene has been reported to decrease oxidative damage, inhibit tumorigenesis, and protect cardiovascular system. In this study, three key genes (crtE, crtI, crtB) involved in lycopene synthesis were co-expressed in Bacillus amyloliquefaciens HZ-12, resulting in a lycopene producing strain HZ-12/pHYcrtEIB. This strain was used to ferment soybean, and the fermentation conditions were optimized. The highest lycopene concentration (7.3 mg/kg) was achieved at 37 °C and initial moisture content of 60%, and the lycopene endowed the red appearance for fermented soybean. Accordingly, the accumulated lycopene significantly improved the antioxidant activity of fermented soybean. Moreover, the fermented soybean showed potent anticoagulant activity, and the anticoagulant activity almost reached 100% when the concentration of soybean extract was 0.4 mg/mL. This study modified B. amyloliquefaciens to produce a novel fermented soybean food with appealing red color and multiple bioactivities, which provided a new and simple strategy for enhancing the functionality of soybean.