| In recent years,with the increased demand for animal protein and the need of its economic development in China,the aquaculture industry got the unprecedented development,but get rich quick development model to make the country's aquaculture industry into the dilemma.At present,the domestic aquaculture tend to be more and more intensive farming mode with high density,eutrophication and other issues arising from the growing,too.Investigate its reason is that in the process of aquatic animal breeding bait lead to the accumulation of excess and their own waste materials such as ammonia nitrogen,nitrite content in the water is too high,it is not only poisoning farmed animals,reduce the immunity,but also can make its infection by bacteria,viruses,directly cause serious economic losses to aquaculture.Biological nitrogen removal efficiency,low cost,and the advantages of small influence on water environment,and thus has great development potential.Aerobic the nitrate bacteria is a kind of can under aerobic conditions by using its own aerobic denitrifying enzyme denitrification of microbes,it compared with the traditional anaerobic denitrifying microorganism,the most essential difference is that it has strong tolerance to oxygen.In the practical breeding,to maintain certain oxygen water,aerobic denitrifying bacteria exploitation and utilization of by people more and more attention.So on aerobic denitrifying bacteria screening and its biological characteristics research has the important meaning of theory and practice in production application and economic value.17 denitrification strains were isolated from mandarin fish pond water of Shanshui city using BTB(bromothymol blue)Spread-Plate Technique.Through the preliminary screening for denitrification strains and determination ability,one aerobic denitrifying bacteria which has strong determination,was named 8F-3.The results showed that the total content of nitrogen was reduced from 100 mg/L to 6.51 mg/L by 8F-3 strain in 24 hours and the rate of denitrification was 93.49%;Ammonia nitrogen was reduced from 50 mg/L to 1.966 mg/L,the removal rate was 96.07%,Nitrate nitrogen was reduced from 50 mg/L to 3.51 mg/L,the removal rate was 92.98%;Nitrite nitrogen was reduced from 0.096 mg/L to 0.071 mg/L,the removal rate was 25.79%.According to the blast results of 8F-3 strain 16 S r DNA sequence(Bootstrap 1000 times)and physiological test for 8F-3 using API method,the bacteria was finally identified as Acinetobacter sp..In order to further explore the denitrification characteristics,this experiment was designed to study the effects of different culture mediums on the growth and nitrogen removal capacity of strain 8F-3.The results showed that the growth and denitrification efficiency of the strains were best when sodium citrate was added as carbon source,potassium nitrate and ammonium chloride compound were added as nitrogen source,and the ratio of C/N = 14.Based on the previous findings,we explored the effects of p H,temperature and agitation frequency on growth and denitrification efficiency.Through orthogonal test,we finally found that the most suitable culture condition is p H = 6.5,temperature = 29 ? and rotation speed = 240 r/min.Under the optimum conditions,the shortest time were 12 h and 16 h when the ammonia nitrogen removal rate reached 99% and the nitrite nitrogen removal rate reached 99% respectively.The bacteria perform well in denitrification in a relatively short time.Therefore it may have certain practical application values in aquaculture and water-treatment. |
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