Effects of poly-ß-hydroxybutyrate (PHB) on Siberian sturgeon (Acipenser baerii) fingerlings performance and its gastrointestinal tract microbial community

Poly-beta-hydroxybutyrate (PHB) is a natural polymer that can be depolymerized into water-soluble short-chain fatty acid monomers. These monomers can act as microbial control agents. In this study, the effects of partially replacing the diet of Siberian sturgeon fingerlings with 2% and 5% PHB were investigated. Replacing 2% of the diet with PHB improved weight gain, specific growth rate (SGR) and survival in the sturgeon fingerlings during the 10-week experimental period. Community-level physiological profiling and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) were used to analyze the microbial community diversity and community organization in the sturgeon gastrointestinal tract. DGGE analysis revealed that PHB affected the intestinal microbial species richness and diversity. The highest species richness was observed with 2% PHB. DNA sequencing of the dominant bands in 2% and 5% PHB treatments revealed that PHB stimulated bacteria belonging to the genera Bacillus and Ruminococcaceae. Principal component analysis, Lorenz curves and the Shannon index of Biolog(TM) Ecoplate data revealed that aerobic metabolic potential of the bacterial community was different in the PHB-treated fishes as compared with the control situation. Overall, our results indicate that PHB act as microbial control agents and replacement of 2% of Siberian sturgeon fingerling diet with PHB has beneficial effects.