Characterization of L. gallinarum Y86: heat-stable antimicrobials and gastrointestinal adaptation

Lactobacillus gallinarum Y86, isolated from broiler ileal mucosa under strict anaerobiosis (85% N₂/10% CO₂/5% H₂), demonstrates significant potential as a microbial feed additive for antibiotic-free farming. 16 S rRNA sequencing (99.79% identity to L. gallinarum ATCC 33199; GenBank ON248243) confirmed its taxonomy. Stationary-phase cultures secreted a heat-stable antimicrobial that produced inhibition zones of 21.53 ± 0.34 mm against Salmonella enterica serovar pullorum and 11.90 ± 0.52 mm against Staphylococcus aureus, retaining 87.30% activity after 120 °C for 15 min; sensitivity to trypsin and lipase indicates a proteolipid nature. Y86 endured pH 2.0 for 3 h (63.37% survival) before programmed lysis at 4 h, then recovered to 92.44% viability under intestinal conditions and maintained 45.36% viability in 0.5% bile. High surface hydrophobicity (85.71%) drove auto-aggregation to 97.99% within 24 h, supporting strong epithelial adhesion. The strain was susceptible to β-lactams, macrolides, and vancomycin, intrinsically resistant to tetracyclines and quinolones, and non-haemolytic, meeting EFSA-QPS safety criteria. Collectively, its thermostable antimicrobial production, timed gastric lysis, intestinal resilience, and proven safety identify Y86 as an industrially compatible candidate for antibiotic-free poultry feeds, advancing microbiota-based alternatives to growth-promoting antibiotics.