Antioxidant, antimicrobial and emulsification properties of exopolysaccharides from lactic acid bacteria of bovine milk: Insights from biochemical and genomic analysis

Exopolysaccharides (EPSs) are versatile organic thickeners derived from microbes, offering beneficial bioactive properties. This study focused on isolating new bacterial strains from bovine milk capable of EPS biosynthesis. Out of 63 isolates, four strains, Lactiplantibacillus sp. ME2b, Lactococcus sp. ME7, Lacticaseibacillus sp. ME17, and Lactobacillus sp. ME27a, exhibited high EPS production, ranging from 0.98 g/L to 2.68 g/L. EPS extracted from these strains had higher carbohydrate and lower protein contents. The EPS extracts showed strong antioxidant activity, demonstrated by DPPH (∼82–89%) and hydroxyl radical scavenging (∼88–91%), and reducing power capacity (3.28–3.65). They also displayed potent antimicrobial activity against Gram-negative and Gram-positive pathogens, including Bacillus cereus, Salmonella typhi, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, with stronger inhibition against Gram-positive strains. Additionally, the EPS showed emulsification activity with ME17 showing the highest emulsification index (60%). The EPS extracts exhibited significant anti-inflammatory effects (∼81–84%). Whole genome sequencing of the prominent strain ME2b revealed a 3,281,666 kb genome carrying 3,101 coding sequences including EPS biosynthesis-related genes epsABCDE, wxz, wzy, and glycosyltransferases. These findings underscore significant potential of the EPS in diverse applications, particularly in food and biotechnology sectors, with future efforts aimed at maximizing EPS capacities for industries and driving innovation across multiple sectors.