Harnessing Bacillus Probiotics: An Approach for Vibrio Pathogen Control and Organic Sludge Management in Shrimp Aquaculture

Abstract

Probiotics are essential in shrimp aquaculture as they help improve water and soil quality, ultimately enhancing productivity. This study assesses the probiotic potential of six Bacillus strains by evaluating various functional traits. The inhibitory activity of culture supernatants from each strain was tested against two Vibrio parahaemolyticus strains and V. vulnificus using a growth kinetics assay. Additionally, the ability of these strains to degrade soil organic matter was evaluated by observing their growth in liquid media containing shrimp pond sludge. The strains were characterized by 16S rRNA sequencing and evaluated for carbohydrate fermentation profiles using an analytical profile index (API) system. Safety assessments included hemolysis, antibiotic sensitivity, and a toxicity assay using Artemia salina. Salinity tolerance was assessed through growth kinetics at varying salt concentrations. Bacillus strains PS1, PS2, and PS5 exhibited significant inhibition against V. parahaemolyticus, while PS1, PS6, and PS5 effectively inhibited V. vulnificus. Strains PS1, PS2, PS5, and PS6 showed strong potential for sludge degradation. Identified as Bacillus pumilus PS1, B. licheniformis PS2, B. subtilis PS5, and B. subtilis PS6, these strains were non-hemolytic and sensitive to common antibiotics, including ampicillin, chloramphenicol, ciprofloxacin, streptomycin, and tetracycline. High survival rates of A. salina in the presence of these Bacillus strains confirmed their safety for shrimp use. Additionally, these strains demonstrated growth across a wide salinity range (5–55 practical salinity units). This study supports the suitability and safety of B. pumilus PS1, B. licheniformis PS2, B. subtilis PS5, and B. subtilis PS6 for shrimp aquaculture applications.