Growth, Acidification Profile and Proteolytic Activity of Thermophilic Lactobacillus spp. Isolated from Traditional Sweet Curd of West Bengal,

Abstract

Microbial fermentation of proteins by lactic acid bacteria offers a promising way to produce bioactive peptides with diverse health benefits. This study evaluated 10 Lactobacillus spp., previously isolated and characterized from traditional Indian sweet curd of West Bengal, for acidification profile, viable counts, proteolytic activity, and free amino acid content. Strains were cultured in skim milk at 42 °C for 24 h and stored at 7 ± 2 °C for 7 days. Peptide production, measured by the o-phthaldialdehyde (OPA) method, showed significant changes during storage. Lactobacillus delbrueckii subsp. indicus (JSL₂P₂) had the highest peptide release (2.63 ± 0.04 mg leucine/ml), while Lactobacillus acidophilus (KM₄) and Lactobacillus salivarius subsp. salivarius (BM₆) had the highest free amino acid concentrations (0.42 ± 0.01 mg leucine/ml) by day 7. These results show proteolysis in fermented milk is dynamic and culture-specific, making starter selection vital for desired nutritional and functional qualities.