In order to explore the optimal fermentation conditions and stability of the antibacterial substances in the supernatant, the plate confrontation method was used to screen antagonistic bacteria with the significant antagonistic effects against Vibrio harveyi, and the salting method with the different ammonium sulfate saturation was performed to extract the crude antibacterial proteins. The results showed that Bacillus velezensis BS2-7 had the most significant antagonistic effects against the aquaculture pathogen Vibrio harveyi GDH11385, the fermentation medium for Bacillus velezensis and fermentation temperature had no significant effects on the antibacterial activity, while the fermentation duration had a significant effect (P<0.05); the supernatant had a wide antibacterial spectrum and showed the antagonistic activity against Vibrio harveyi, Vibrio owensii, Vibrio parahaemolyticus, and Bacillus altitudinis; the temperature, pH, and ultraviolet irradiation had significant effects (P<0.05); when the ammonium sulfate with 10% saturation and 20% saturation were added into the supernatant, the crude proteins separated from the fractions had the antibacterial activity against Vibrio harveyi and Vibrio owensii. Our findings provide the sample support and the theoretical basis for the development of antibacterial protein drugs against Vibrio pathogens.

In the report, in order to alleviate the environmental pressure caused by farming activities, a model that intelligently integrated industrialized recirculating aquaculture with Small Greenhouse-Shrimp Farming Systems of Litopenaeus vannamei was proposed, in which the combination of 6 strain microalgae and 3 strain bacteria which were isolated and screened from Small Greenhouse-Shrimp Farming Systems of Litopenaeus vannamei in Guangdong Province was discussed, and their effects on the reduction of COD, TN and TP in aquaculture tailwater were evaluated. The results indicated that the Enterococcus gallinarum and Chlorella sp. CH33 yielded the optimal water purification results with removal rates of COD, TN, and TP in aquaculture wastewater reaching 83.56%, 94.52%, and 91.68% respectively, which were significantly superior to that of single microalgae and other microalgae-bacteria combinations (P<0.01), especially, in TN removal. Our findings provide a theoretical basis and technical support for improving existing aquaculture models, which contribute to the promotion of sustainable development of the aquaculture industry.