Abstract:Shrimp aquaculture, as one of the main components of the aquaculture industry, has produced enormous economic benefits and social benefits. But the sustainable development of the shrimp aquaculture has been affected and restricted by the discharge of the waste and the frequent occurrence of diseases. Bio-floc technology by adding brown sugar, molasses and other carbon source in breed pool to promote heterotrophic microbial growth and reproduction to control the water pollution, shows great prospects for development in shrimp culture. In this study, we established a method of simplified fermentation that used a strain of Bacillus megaterium with the activity of denitrification. And we used prawn feed and brown sugar as the medium. Results showed that the best ratio of medium was prawn feed 3 g/L, brown sugar 6 g/L and inoculation volume 1×108 CFU/ml through the orthogonal experiment. And the other conditions were optimized by single experiment. We got the fermentation products with the viable cell number was 1.16×1010 CFU/ml that fermented with 31℃, 40% liquid volume and 24 hours. Then we fed the Litopenaeus vannamei through the bio-floc technology by using the fermentation products. The result showed that the volume of bio-floc was formed more quickly in dominated bio-floc group (added bacillus and sugar) than bio-floc group (just added sugar) and control (traditional culture pattern) (P<0.05), and the overall concentration level of nitrite-N in dominated bio-floc group was much lower than the other groups (P<0.05). At the end of the culture, the highest of the average body length and weight in prawns was obtained in dominated bio-floc group, and Bio-floc group and control were significantly lower (P<0.05). This study established a simplified and feasible method for the fermentation of probiotic bacteria. And the results showed the effectiveness of the bio-floc technology in prawn culture is verified by the additiong probiotics.
