The Fermentation Techniques For Bacillus Firmus With Agriculture Byproducts And The Microorganism Diversity Of Biofloc Cultured With Bacillus Firmus

Since 1990s, the shrimp culture of china has great developed in the effort of government, researchers and farmer. China has became the largest shrimp output country all over the world. Probiotics get more and more attention which are widely used in the aquaculture industry. Probiotics are used to improve culture enviroment, restrain the multiplying of pathogen and enhance the immunity of cultured animals. The widely use of probiotics has created huge economic efficiency. Biofloc are composed of microbe mass. The biofloc formed by probiotics have good effect and application value.In this study, we use Bacillus firmus isolated from shrimp intestine to research microbe fermentation technology using in biofloc aquaculture beside culture pond. In the premise of low cost, agriculture byproducts (straw, wheat bran, soybean meal, peanut meal, corn flour) were used as the fermentation media. The favorable media formulation and fermentation conditions were optimized by the orthogonal tests and single factor experiments. The results will provide theoretic basis and key technique support for aquaculture.Biofloc aquaculture, which can solve the problems of water pollution and environment deterioration in high density aquiculture, has got more and more attention. Nowadays, lots of researchers concentrate on the addition value of biofloc, especially on the pathogen control. In this study, Bacillus firmus, carbon source and nitrogen source were added into water to control the dominant bacteria and the microbe diversity of biofloc and change of composition when developing were also studied by DGGE. The differences of control group without Bacillus firmus and experimental group were also analyzing in this technique.The research of fermentation techniques for the production of Bacillus firmus with agriculture byproducts show that using straw, wheat bran, soybean meal, peanut meal, corn flour as the fermentation media, the collocation of straw, wheat bran and peanut meal are suitable for growth of Bacillus firmus . The fermentation of the bacteria reached the best results with the optimized media formulation, which contains 1.8% straw, 4% wheat bran, and 0.6% peanut meal, under the condition of temperature 36°C, initial pH at 6.0, filling rate 50% for 60h fermentation.The result of microbe diversity of biofloc strengthen with Bacillus firmus show that when adding Bacillus firmus fermented with straw, bran, and peanut meal and necessary carbon and nitrogen sources to the culturing water, in the condition of aeration and 30℃, biofloc in experimental group did not yield very much in the first four days. The biofloc appeared rapid growth since the 4th day, and biofloc reach the maximum amount in the 7th day and keep stable. In the control group without Bacillus firmus, culture water became turbid in the 3th day, but no biofloc formated during these days. There was a little biofloc formatting since the 6th day. The density of biofloc in the control group was low and biofloc floated in the water.In this study, the the differences of microbial diversity between control groups and experimental groups are analyzed by DGGE. The results show that some stripes of predominant bacteria disappear in the forming process of biofloc. The microbial competitive growth in the forming process of biofloc leads to this phenomenon. There are different stripes in the control groups and experimental groups. The phenomenon indicates that adding Bacillus firmus to the culture water influences the structure of microbial community. After TA clone of target gene, the plasmids are sent to sequencing company for being sequenced. The results show that biofloc in this study contains Pseudomonas sp.,Verrucomicrobia ,Cyclobacterium sp., Stenotrophomonas sp. and some uncultured bacterium. Bacillus also can be identified in the experimental groups.