Application of poly-β-hydroxybutyrate (PHB) in mussel larviculture

In this study, the effect of poly-β-hydroxybutyrate (PHB) delivery on the performance (survival, growth and metamorphosis) of blue mussel (Mytilus edulis) larvae was studied for the first time. Upon addition of PHB in either crystalline (i.e. extracted from the bacterial cell) or amorphous (i.e. still contained in the bacterial cell) forms to a standard algal diet at concentrations of 0.1mgL−1, 1.0mgL−1 and 10.0mgL−1, no significant improvement in growth performance or metamorphosis was observed. However, a concentration of 1.0mgL−1 amorphous PHB almost doubled the survival of the larvae in several independent experiments. A total of sixteen PHB-degrading bacterial strains belonging to genus Pseudoalteromonas could be isolated from the PHB treated mussel larvae. The application of these in combination with PHB however, did not further increase the culture performance of the mussel larvae. Where previous studies suggested that the PHB effect could be related to a change in the intestinal microbial community of the treated animals, molecular fingerprinting analysis of the mussel larvae associated microbiota did not show a relationship between changes in the microbiota composition and the improved survival following PHB treatment. Overall, this study showed for the first time that PHB can be applied in blue mussel larviculture to increase the survival of the cultured animals.