Bioactive peptides from fermentates of soy protein and whey protein isolates: A comparative study

This study explores the antidiabetic and anti-inflammatory activities of polypeptides from fermented whey protein isolate (WPI) and soy protein isolate (SPI) using Limosilactobacillus fermentum (KGL4) MTCC 25515. Both fermented WPI and SPI demonstrated significant α-amylase and α-glucosidase inhibition, with SPI showing higher inhibition rates. Proteolytic activity peaked at 48 h and a 2.5% inoculation rate, with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and two-dimensional (2D)-PAGE revealing changes in protein profiles and peptide distribution. Ultra-filtered fractions, particularly the 3 kDa permeates, exhibited strong antidiabetic effects. Furthermore, fermented WPI and SPI reduced nitric oxide production and pro-inflammatory cytokines in RAW 264.7 cells without causing cytotoxicity at 2 mg/mL concentrations. Confocal microscopy showed that fermentation led to the formation of smaller peptide structures, suggesting that KGL4-fermented WPI and SPI are promising sources of bioactive peptides with potential applications in functional foods and therapeutics.