Abstract:In recent years there have been a number of outbreaks of lethal shrimp diseases caused by viral and bacterial infections in many countries, which hinders the development of shrimp culture industry. To protect shrimp from diseases, a lot have been done to improve the shrimp germplasm against disease, the shrimp culture technology, as well as the aquaculture environment. One example is the bioflocs technology (BFT) that helps eliminate harmful nitrogen sources, reduce water exchange rate, and increase the feed utilization rate. Probiotics such as Bacillus sp. could also improve water quality in the shrimp culture pond. In this study, we isolated a strain named 2013042402 (Strain 02) from a shrimp pond. Strain 02 was identified as Bacillus sp. using 16S rDNA sequencing and gas chromatographic analysis of the whole cell fatty acids. To investigate the function of Strain 02 in bioflocs for the shrimp culture system, we added three groups into the culture system that were Strain 02(2.0×104 CFU/ml) combined with sucrose (70% of feed), strain 02 alone, and sucrose alone. Then we measured a series of physicochemical parameters of the culture system including temperature, salinity, dissolved oxygen, pH, floc volume, ammonia-N and nitrite-N. We also examined the growth rate and the survival rate of shrimps, and the compositions of dominant bacterial communities in the water body. We found that the Strain 02-sucrose combination significantly reduced the concentrations of ammonia-N and nitrite-N in the water and improved the survival rate and growth rate of shrimps. This suggested that Strain 02 added to the bioflocs could improve the aquaculture water quality, optimize the structure of bacterial communities, and inhibit the growth of vibrio, therefore elevate the survival rate and growth rate of shrimps. Our study implied that the bioflocs technology could be highly improved by the addition of probiotics.
