Potential of LP as a Biocontrol Agent for Vibriosis in Abalone Farming.

Vibrio species are among the primary pathogenic bacteria affecting abalone aquaculture, posing significant threats to farming practices. Current clinical control predominantly relies on antibiotics, which can result in antibiotic residues in both abalone and the surrounding marine environments. Lactobacillus plantarum (LP) has been shown to release bioactive antagonistic substances and exhibits potent inhibitory effects against marine pathogenic bacteria. This study aimed to screen and characterize the probiotic properties of LP strains isolated from rice wine lees to develop a novel biocontrol strategy against Vibriosis in abalone. The methods employed included selective media cultivation, streak plate isolation, and single-colony purification for strain screening, followed by Gram staining, 16S rDNA sequencing, and phylogenetic tree construction using MEGA11 for identification. The resilience, antimicrobial activity, and in vivo antagonistic efficacy of the strains were evaluated through stress tolerance assays, agar diffusion tests, and animal experiments. The results demonstrated the successful isolation and purification of four LP strains (NDMJ-1 to NDMJ-4). Phylogenetic analysis revealed closer genetic relationships between NDMJ-3 and NDMJ-4, while NDMJ-1 and NDMJ-2 were found to be more distantly related. All strains exhibited γ-hemolytic activity, bile salt tolerance (0.3-3.0%), and resistance to both acid (pH 2.5) and alkali (pH 8.5), although they were temperature sensitive (inactivated above 45 °C). The strains showed susceptibility to most of the 20 tested antibiotics, with marked variations in hydrophobicity (1.91-93.15%) and auto-aggregation (13.29-60.63%). In vitro antibacterial assays revealed that cell-free supernatants of the strains significantly inhibited Vibrio parahaemolyticus, V. alginolyticus, and V. natriegens, with NDMJ-4 displaying the strongest inhibitory activity. In vivo experiments confirmed that NDMJ-4 significantly reduced mortality in abalone infected with V. parahaemolyticus. In conclusion, the LP strains isolated from rice wine lees (NDMJ-1 to NDMJ-4) possess robust stress resistance, adhesion capabilities, and broad antibiotic susceptibility. Their metabolites exhibit significant inhibition against abalone-pathogenic Vibrios, particularly NDMJ-4, which demonstrates exceptional potential as a candidate strain for developing eco-friendly biocontrol agents against Vibriosis in abalone aquaculture.