A novel fermented soybean, inoculated with selected Bacillus, Lactobacillus and Hansenula strains, showed strong antioxidant and anti-fatigue potential activity.

The aim of this study was to develop a novel fermented soybean food (FSF) using selected Bacillus subtilis GD1, Bacillus subtilis N4, Bacillus velezensis GZ1, Lactobacillus delbrueckii subsp. bulgaricus and Hansenula anomala, as well as to assess its antioxidant and anti-fatigue activity. These Bacillus strains had excellent enzyme producing and soybean transformation capacity. FSF showed the highest peptide, total phenol, total flavonoid content, antioxidant activity, and suitable organic acid and biological amine content. In intense exercise mice, FSF treatment markedly increased hepatic glycogen level, decreased metabolite accumulation, improved the activities of antioxidant enzymes and decreased malondialdehyde (MDA) level in serum and liver, respectively. Furthermore, FSF treatment increased nuclear factor-erythroid 2-related factor 2 (Nrf2) and antioxidant response element (ARE)-dependent gene expression. Together, the selection of microbial starter culture and mixed culture fermentation are essential for the effective enrichment of bioactive compounds, and FSF has stronger antioxidant and anti-fatigue activity.