Screening and isolation of PHB (Poly-β-hydroxybutyrate) producing bacteria as an alternative material for disease prevention on the shrimp culture

The shrimp mortality cases in ponds are still dominated by the bacterial diseases caused by Vibrio pathogenic bacteria. Antibiotic application as a disease alternative treatment is not recommended because it can trigger the host immunity and cause residual contamination in the environment. The latest study stated that poly P-hydroxybutyrate (PHB) has bactericidal activity against the pathogenic bacteria and can be a source of C (carbon) atoms that are easily decomposed by the bacterial intestinal flora. This ability is obtained from the short-chained fatty acids (butyric acid) in PHB compounds. This study was aimed to screen and isolate the candidates of PHB-producing bacteria as an alternative to control environmentally friendly disease prevention in shrimp culture. Sampling was performed at the camming sugar factory located in Bone. Samples were taken in the form of kettle ash, molasses, the soil around the factory site, bagasse, and solid sugar factory waste. Samples were serially diluted using a sterile aquadest and grown on the nutrient agar media, then incubated for 48 hours. After 48 hours, the morphological observations were performed for each bacterial colony growing in each analyzed sample. The isolation of PHB-producing bacterial candidates was performed by isolating triplicate colonies and cultured on agar nutrient (NA) media added with 1% glucose, then incubated for 48 hours. The growing bacterial colony was recultured on a spot of NA media through plating divided into 4 equal parts and incubated for 48 hours. Each colony was given an ethanolic 0.02% Sudan Black B solution and stood for 30 minutes, then rinsed with 96% ethanol. The positive results of PHB-producing bacteria were shown in dark blue color absorbed by the bacterial candidate due to the staining performed. The study results showed that 73 isolates of PHB-producing bacterial candidates were obtained from 5 samples analyzed and after stained with Sudan Black obtained 14 bacterial isolates containing 10 isolates produced a clear zone (inhibition zone) and 4 isolates absorbed the dark blue color. After purification and retesting on the 14 isolates, 5 isolates were obtained as candidates for PHB-production bacteria.