Proteolytic and Functional Changes During Whey Fermentation by Lactococcus lactis NCFB 724: An Integrated Analysis of ACE and DPP-IV Inhibitory Activities

Bioactive peptides derived from food proteins have gained attention as potential functional food components. This study evaluated proteolytic and functional changes during whey fermentation with Lactococcus lactis NCFB 724, with emphasis on the in vitro inhibition of angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV). Whey was fermented for 48 h, monitoring microbial growth, pH, titratable acidity, free amino group concentration, electrophoretic profile, and ACE- and DPP-IV-inhibitory activities. Pearson correlation analysis and principal component analysis (PCA) were additionally performed as exploratory approaches. During fermentation, pH decreased from 6.07 to 4.00, while cell viability increased from 5.9 to 8.8 log CFU/mL and free amino group concentration increased from 407.02 to 539.20 µg/mL. Electrophoretic analysis revealed changes in signal distribution in the low-molecular-weight region (<10 kDa). DPP-IV-inhibitory activity showed no significant differences among fermentation times, with values of 35.49% at 0 h and 37.80% at 48 h, whereas ACE inhibition showed a time-dependent response, reaching its highest value (57.14%) at 24 h. The first two principal components explained 82.69% of the total variance, providing an exploratory visualization of the temporal patterns among the evaluated variables. Overall, greater proteolysis did not correspond to greater enzyme-inhibitory activity. These findings identify 24 h as a fermentation stage of interest for further characteriza tion.