Probiotic properties of bacillus subtilis isolated from dried anchovies (Stolephorus indicus) and evaluating its antimicrobial, antibiofilm and growth-enhancing potential in danio rerio

Abstract

The study was aimed at isolating and characterising a potential probiotic bacterium from dried anchovies (Stolephorus indicus) and evaluating its antibacterial, antibiofilm and growth enhancing potential in Danio rerio. The isolate was identified as Bacillus subtilis using 16S rRNA sequencing and phylogenetic analysis. Probiotic properties were characterised based on the ability of the isolated strain to survive in simulated gastric juice and trypsin. Isolated strain was further subjected to varying pH, temperature, different concentrations of organic solvents to evaluate its potential to tolerate stress. Biofilm inhibition against Vibrio harveyi (31.5±4.6%), Escherichia coli (28.8±4.2 %), Pseu-domonas aeruginosa (34.8±3.1%) and Staphylococcus aureus (34.4±3.75%) was noted. The study showed that the isolate improved the survival rate of Danio rerio against Vibrio harveyi and Escherichia coli. The weight (12.77±0.06) and length (11.413±0.18) gain percentage was numerically (p> 0.05) improved in probiotic supplemented groups as compared to control. The use of probiotics from non-conventional sources can improve the diversity of the available probiotics for aquaculture practices.