Menaquinone-7 enhancement, coordinated control of biogenic amines, and flavor modulation in natto: Development of a food safety-oriented fermentation strategy

Abstract

Natto, a nutritionally dense fermented soybean product, has been found to contain various health-promoting components, including nattokinase and menaquinone-7 (MK-7). In contemporary natto production, Bacillus subtilis was commonly used as a starter culture to ensure stable quality. However, this approach overlooked the enhancement of beneficial compounds, the coordinated control of biogenic amines during fermentation, and their positive impact on natto's quality, flavor, and bioactivity. In this study, B. subtilis var. natto (designated as the NC group) and MK-7-producing B. subtilis var. natto BSN01 (designated as the NE group) was used as a starter culture to ferment natto. The results demonstrated that the nutritional quality of natto was improved after fermentation. The NE group had the highest MK-7 content ever reported, with a value of 2.05 ± 0.05 mg/100 g, which was 2.86-fold higher than that of NC group. The accumulation of biogenic amines during fermentation remained within the safe control range. Additionally, the flavor of the natto was also significantly improved, along with a greater variety and higher concentrations of typical volatile compounds, such as 2,5-dimethyl pyrazine, and trimethyl-pyrazine, which imparted roasted meat aroma and nutty fragrance to natto. Furthermore, it displayed excellent in vitro antioxidant, thrombolytic, and anticoagulant activity. In conclusion, this study highlighted the beneficial role of the MK-7-producing strain B. subtilis var. natto BSN01 in natto production and the coordinated control of biogenic amines, offering a valuable, food safety-oriented fermentation strategy.