An In Vivo and In Vitro Assessment of the Probiotic Potentials of Indigenous Halotolerant Bacteria on Growth Performance and Digestive Enzymes of White Leg Shrimp (Litopenaeus vannamei) in High-Salinity Waters

Abstract

The present study was aimed at evaluating Bacillus subtilis subsp. inaquosorum strain IS02 (B.s.i. IS02; GenBank accession number: JN856456.1) to determine the growth kinetics of antimicrobial metabolite production in different ranges of environmental factors, such as salinity (15-55‰), pH (5-9), and temperature (30-40°C); to evaluate the lifespan of antimicrobial metabolites in different ranges of salinity (0-57‰), pH (2-12), and temperature (35-121°C); and to investigate the effect of B.s.i. IS02 as an additive to functional feed on the digestive activity of Litopenaeus vannamei under high-salinity conditions. Based on the present findings, the bacterium maintained its antimicrobial properties up to 45‰ salinity ( $10729.93\pm 23.93AUm{l}^{-1}$ ). There was no significant difference in the antimicrobial activity of metabolites at 35°C and 40°C ( $p>.05$ ). In the experimental trials, the shrimp postlarvae were fed different concentrations of B.s.i. IS02 (106, 107, and 108 CFU kg-1 diets) under high-salinity (>55‰) conditions. The activity of digestive enzymes, amylase, lipase, and protease in the probiotic-fed shrimp postlarvae was significantly higher than that of the control group ( $p<.05$ ). The present findings revealed that B.s.i. IS02 maintained the antimicrobial metabolite production, retained the antibacterial lifespan in high-salinity waters, and improved the growth and digestive enzyme activities of shrimps.