Isolation, Identification And Application Of Effective Microorganisms In Marine Aquaculture

With the rapid development of China’s aquaculture industry, aquaculture scale disease occurs occasionally. Drug abuse destroys the micro ecological balance in aquaculture water, while antibiotics residues are still a threat to human health.These problems limit the development of aquaculture industry greatly. And the large-scale intensive farming produces large amounts of waste water. The waste water carries large amounts of residual bait and aquaculture waste.And discharging this raw sewage into the open waters directly has not only polluted the water environment, destroyed the ecological balance of the waters surround the farms, but also has caused the second pollution of the aquaculture water. The aquaculture water, which nitrogen content is too high, can lead to a large number of organisms’ death when it is serious. Therefore, how to deal with these problems has become the key to improve the economic benefits of aquaculture.Probiotics which derive from nature are the general designation of the bacteria who has probiotic effect.They have the function of inhibit the growth of harmful bacteria, improve the host immunity, provide nutrients, and purify water. And probiotics have the advantages of low production cost, strong adaptability, environmentally friendly, and easy to use.These advantages make probiotics become the focus of the aquaculture health management.This research used the probiotics, which isolated and stored in the laboratory, to improve the water quality and strengthen the resistance of the aquaculture animal disease.During the experiments, we worked on the effect of the organisms survival rate,growth rate and water quality caused by using the probiotics alone or in groups in the Scophthalmusmaximus fries breeding. We also selected a new microbe which had heterotrophic ammonia oxidizing bacteria and aerobic denitrification,and did some research about its performance of high-efficiency denitrification.The results were as follows:1. Through the activated culturing light Photosynthetic Bacteria(Thiophilic Red Oomycetes), Chlorella sp., bacillus and Lactobacillus helveticus that were separated and preserved in our laboratory, we cultured them in scale, and collected the bacteroids. And then applied the beneficial becterias in the Turbot(Scophthalmusmaximus) seedlings breeding experiment alone or combined with Lactobacillus helveticus two agents.In the process of the experiment of 5 weeks, the results showed that feeding Lactobacillus helveticus could significantly improve the survival rate of turbot seedlings.The first three weeks, the survival rates were higher than those of the control group by 13,10 and 11%, respectively. When stop feeding Lactobacillus helveticus, the survival rate decreased significantly after two weeks. Feeding Bacillus turbot separately, the survival rate was significantly higher than that that of the control group. The survival rates of three weeks were higher than those of the control group by 3,10 and 11%, respectively. The survival rate was still high when stop feeding after two weeks,15% higher than that of the control group. Three weeks ago, for the photosynthetic bacteria treatment group of juvenile turbot, the survival rate was also significantly higher than that of the control group, but the survival rate decreased significantly after stopping to use the photosynthetic bacteria. While, for the treatment of Chlorella alone group turbot, the survival rate was significantly lower than that of the control group. Using photosynthetic bacteria alone might be favorable to reduce the ammonia nitrogen content in water. Combined with Chlorella, Bacillus and Swiss milk, it could make the Turbot(Scophthalmusmaximus) survival rate increase by 12%, and the weight gain rate increased by 13%. Combined with Lactobacillus helveticus and bacillus, it could improve the final weight, higher than 10.8%in the control group.2. We activated 200 strains of heterotrophic bacteria that were taken from Qingdao coastal seawater and the South China Sea. Through the screening and the second screening test of ammonia oxidation, nitrification and denitrification, we identified significant ammonia oxidation effect of Q6, Q45, Q45-2, Luf 99, S1, S3, S12, S22, F6 and F7 of ten strains of marine bacteria.3. The addition of organic nitrogen source was peptone and yeast extract could promote the growth of strain Luf 99. Under heterotrophic conditions, pH7.5-8.0, 25-30℃, it could grow quickly in the aerobic culturing, and was capable of degrading ammonia nitrogen. The strain growth reached the peak in 48h. In the ammonia oxidation performance test of strain Luf 99, we found that different C/N ratio could significantly affect the ammonia oxidation ability of strain Luf 99. Among all, the 15:1 and 10:1 C/N ratio had the highest ammonia nitrogen removal rate, while the C/N 1:6 the highest removal rate per hour of ammonia nitrogen ratio. The C/N ratio going too high or too low would both affect the strains of ammonia removal efficiency. But when C/N was low, the removal rate per hour became higher.