Structural Properties and Antioxidant Activities of Soybean Protein Hydrolysates Produced by Lactobacillus Delbrueckii Subsp. Bulgaricus Cell Wall Proteinase

Abstract

This study investigated the structural and biological properties of soybean protein isolate (SPI) after 0-8 h hydrolyzation with cell wall proteinase (CEP) extracted from Lactobacillus delbrueckii subsp. bulgaricus. CEP hydrolysis increased the β-turn and β-sheet content and red-shifted the fluorescence peak, while decreasing the α-helix content, indicating the unfolding of SPI proteins. Increased surface hydrophobicity and fluorescence of the SPI hydrolysates were correlated with increased hydrophobic amino acid content (from 209.67 to 217.6 mg/100 g). CEP tended to hydrolyze the N- and C-terminal regions of peptide sequences dominated by Gly and Leu, which enhanced the antioxidant activity of the SPI hydrolysates (lowest IC 50s after hydrolysis for 4 h). Comparison with the database of bioactive peptides suggested various potential biological activities, including antioxidant activity, angiotensin-converting enzyme inhibitory activity and dipeptidyl peptidase-IV inhibitory activity. The study findings have theoretical significance for the development of CEP hydrolysis and novel bioactive soybean peptides.

Keywords: Soybean protein isolate, Lactobacillus delbrueckii subsp. bulgaricus, cell wall proteinase, structural properties, antioxidant activity