Abstract
Lentils are recognized as sustainable alternative protein sources due to their favorable nutritional and functional profiles. This study evaluated the protein quality and digestibility of raw (RRLPI) and fermented (FRLPI) red lentil protein isolates and assessed their impact on the gut microbiota using the SHIME® in vitro dynamic gut model. Fermentation significantly increased in vitro protein digestibility (IVPD), from 92.5 % in RRLPI to 94.5 % in FRLPI (p < 0.05). Amino acid profiling revealed that while sulfur-containing amino acids decreased, threonine and other key essential amino acids were better preserved or enriched in FRLPI when expressed per gram of protein. Feeding with FRLPI promoted the growth of potentially beneficial colonic genera such as Lactiplantibacillus and Furfurilactobacillus and stimulated short-chain fatty acid (SCFA) production, with a notable increase in butyrate. Moreover, FRLPI digestion yielded a greater release of low-molecular-weight peptides (<3 kDa), some of which exhibited predicted antioxidant and ACE-inhibitory activities. Together, these results highlight fermentation as a strategy to optimize lentil protein functionality, improving gut microbial ecology, nutrient bioavailability, and the release of health-relevant peptides.