No abstract

Actinomycetes, as the main producers of a variety of active metabolites and enzymes, have received extensive attention in aquaculture. An actinomycete had been isolated from Haizhou Bay and been identified by morphological analysis and 16S rRNA sequencing. Results showed that the actinomycete had the highest similarity (99.65%) with Nocardiopsis sp. and was named strain E10. Strain E10 produced an exo-enzyme with proteinase effect that showed strong antibacterial activity against Vibrio anguillarum. This strain E10 was tested as a probiotic for the culture of Exopalaemon carinicauda. After having been fed with a diet supplemented with strain E10 for 30 days, the final body weight (Wt), weight gain rate (WGR), special growth rate (SGR), survival rate (SR) and digestive enzymes (chymotrypsin, α-amylase and lipase) of E. carinicauda in all experimental groups showed no significant differences (). However, the antioxidant enzymes (total superoxide dismutase, catalase and peroxidase) and the non-specific immune-related enzymes (acid phosphatase, alkaline phosphatase and lysozyme) in the treatment groups increased significantly () compared with the control group. The cumulative mortality of the treatment groups (35.56% in 5 × 109 CFU/100 g) was significantly lower than that of the control treatment (73.33%) () post challenge with V. anguillarum for 14 days. The results indicated that strain E10 had no significant effect on the growth, but a significant improvement on the immunity of E. carinicauda. This study provides the data for ecological aquaculture of E. carinicauda.