Enhancement of Antioxidant Activity and Bioactive Compounds in Soy Whey Fermented with Lactiplantibacillus plantarum and Weissella confusa

Abstract

Soy whey (SW) is a byproduct from tofu and soy protein isolate (SPI) production that contains various nutrients such as protein, amino acids, minerals, carbohydrates, isoflavones. In this study, SW was fermented with lactic acid bacteria (LAB) with the aim to enhance total phenolic contents (TPC), Gamma amino butyric acid (GABA) and antioxidant activity. Eight different LAB strains were selected and the activity and cell counts of the most potent strains were investigated during fermentation. The results showed that all the isolates were able to grow in SW and the increase in incubation time led to significantly (p<0.05) decrease the pH of all samples from 5.75 to 4.5. Among eight LAB isolates, Lactiplantibacillus plantarum MCM4 and Weissella confusa MDM8 showed higher activity in terms of acid production, increase in TPC content and proteolytic activity. The sample fermented by L. plantarum MCM4 had the highest content of free amino acids (1.73 mg/ml) and the unfermented sample with 0.9 mg/ml had the lowest content. GABA concentration varied from 6.15 mg/mL (unfermented) to 24.175 mg/100 mL (SW fermented with L. plantarum MCM4). In this research, it was found that fermentation increased the antioxidant capacity of SW in such a way that the highest amount was observed in sample fermented with Lactiplantibacillus plantarum MCM4. A positive correlation (R2= +0.72) was found between viable cell counts and proteolysis. It can be concluded that, fermentation with L. plantarum MCM4 and W. confusa MDM8 can be applied as an approach to valorize SW.

Keywords

• biorefinery
• fermentation
• gamma aminobutyric acid
• lactic acid bacteria