Effects of submerged liquid fermentation of Bacillus subtilis WX‐17 using okara as sole nutrient source on the composition of a potential probiotic beverage

This work aims to produce a functional probiotic beverage using okara as the sole nutrient source. Hence, okara was fermented with Bacillus subtilis WX‐17 in submerged liquid fermentation and the supernatant was tested. Metabolomic analysis showed that the nutritional profile of the beverage was enhanced after fermentation. Essential amino acids as well as short‐chain fatty acids were significantly (p < .05) upregulated. Total phenolic content and antioxidant content (in terms of DPPH radical scavenging activity) increased by 6.32 and 1.55 times, respectively. After 6 weeks, probiotic viability remains unchanged when stored at 4°C and the cell count is above the minimum dosage to confer health benefits. Antimicrobial activity was also detected against gram‐positive bacteria. The findings of this work showed the potential of submerged liquid fermentation of Bacillus subtilis WX‐17 using okara as sole substrate to produce a functional and low‐cost probiotic beverage.