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.
Keywords: Bacillus subtilis; Metabolomics; antimicrobial activity; antioxidant activity; okara; probiotic beverage; submerged liquid fermentation; total phenolic content.
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