Polyhydroxybutyrate (PHB) From Biofloc Systems Enhances the Growth and Immune Performance of Genetically Improved Farmed Tilapia

This study characterised polyhydroxybutyrate (PHB)‐producing bacteria from the culture water of genetically improved farmed tilapia (GIFT) in biofloc ponds and investigated the influence of PHB on the growth and immune performance of GIFT. Out of 40 bacterial isolates, Bacillus infantis , Exiguobacterium profundum , Bacillus subtilis , Bacillus megaterium , Klebsiella pneumoniae and Enterococcus hirae showed positive results for PHB against fluorescent stains. The PHB yield in the range of 5%–95.45% (w/w) was recorded, with the highest from K. pneumoniae (95.45% w/w). The experimental treatments included a basal diet as a control (C), a basal diet with PHB (5 g kg −1 ) from K. pneumoniae (T1) and a basal diet with PHB (5 g kg −1 ) from E. hirae (T2) for 60 days. Diet T1 had the best weight gain (131.2 ± 0.6), SGR (3.36 ± 0.33) and FCR (2.02 ± 0.24), with a significant difference between the control and PHB diets ( p < 0.05). Diet T1 showed higher serum protein with improved myeloperoxidase, respiratory burst activity, catalase, superoxide dismutase and glucose levels. The relative percent survival (RPS) of the fish subjected to Aeromonas hydrophila (10 7 CFU/mL/fish) was highest in T1 (80.95%), with no significant difference between the treatments ( p > 0.05). The results of this study confirm the presence of PHB‐producing bacteria in the biofloc system, providing a basis for increased PHB production for application in aquaculture and the positive effect of extracted PHB on the growth and immune response of GIFT.