Enhancing natto quality by co-fermentation with Pediococcus pentosaceus PP04 and Bacillus velezensis BV702: Nattokinase activity, nutritional profile, and flavor characteristics

Bacillus spp. are the main nattokinase (NK) producers, but monoculture fermentation often causes an unpleasant ammoniacal odor. This study first selected B. velezensis BV702 as a starter strain based on NK activity and sensory evaluation, and then introduced probiotic Pediococcus pentosaceus PP04 for co-fermentation to improve natto quality. The results demonstrated that under optimal conditions (strain ratio 1:2 [PP04:BV702], inoculation amount 5 %, fermentation temperature 37 °C, time 24 h), NK activity (3050 U/g) and sensory scores of natto were significantly enhanced. Mixed fermentation increased the essential amino acid content (582.79 mg/100 g) while reducing bitter amino acids. Volatilomics analysis revealed elevated levels of esters and characteristic flavor compounds (e.g., acetylpyrazine and 2-ethyl-3,5-dimethylpyrazine) in co-fermented natto. Notably, fruity, sweet, and nutty flavors intensified, whereas fatty and waxy odors diminished. This study provides insights into probiotic applications in natto production. • Bacillus velezensis BV702 is characterized by high nattokinase production. • Co-fermentation of P. pentosaceus PP04 and BV702 enhances nattokinase expression. • Co-fermentation of BV702 and PP04 enhanced natto's flavor and nutritional value.