Screening,Identification And Characterization Of Highly Efficient Nitrogen-removing Bacteria

Good water environment is the key to realize healthy aquaculture.In recent years,due to the increase of aquaculture density,the harmful substances such as ammonia nitrogen,nitrite nitrogen,and BOD accumulated with a large amount of compound feed,which led to the destruction of water ecological environment and seriously affected the sustainable development of aquaculture.Biological nitrogen removal method is widely used because of its advantages of high efficiency and no secondary pollution.As a new biological nitrogen removal technology,heterotrophic nitrification-aerobic denitrification bacteria has become a research hotspot at home and abroad.In this study,a heterotrophic nitrification-aerobic denitrification strain with high nitrogen removal efficiency was isolated from intensive culture ponds.The genus of the strain was determined through morphology,physiological and biochemical tests,and 16 S r DNA identification.The characteristics of heterotrophic nitrification,aerobic denitrification,and nitrogen removal in mixed nitrogen were studied.The main results were as follows.1?A strain DW-10 with heterotrophic nitrification-aerobic denitrification ability was screened from intensive pond sediment.The strain DW-10 was identified as Acinetobacter variabilis DW-10 by morphological observation,physiological and biochemical test,and 16 S r DNA sequence alignment analysis.2?The effects of carbon sources,ammonia nitrogen concentration,C/N,initial p H value,and rotating speed of shaking table on heterotrophic nitrification of DW-10 were studied.The results showed that under the conditions of sodium acetate as the sole carbon source,ammonia nitrogen concentration of 150.0 mg/L,C/N=10,p H 7.0,culture temperature 25 ? and rotating speed of the shaking table 190 r/min,ammonia nitrogen removal rate and removal rate were 99.69±0.03% and 7.16 mg/L/h respectively.3?The aerobic denitrification characteristics of strain DW-10 were investigated using a single factor test.The strain DW-10 was able to carry out aerobic denitrification using nitrite or nitrate nitrogen as the only nitrogen source.Under the conditions of sodium acetate as carbon source,C/N=10,initial p H of medium 8.0,and temperature of 25 ?,the rotational speed was as follows The highest removal rates of nitrite and total nitrogen were 92.92±0.67%,75.48±4.98%,190 r/min,respectively.and when the incubation temperature was30 °C and the rotational speed was 170 r/min,the degradation rate of nitrate and total nitrogen was maximum.73.99 ± 9.90% and 56.95 ± 7.02%,respectively.4?The denitrification characteristics of strain DW-10 in the mixed nitrogen sources system were studied.The results showed that the strain ammonia nitrogen preferentially was used for heterotrophic nitrification and aerobic denitrification in the mixed nitrogen sources system of ammonia nitrogen,nitrate nitrogen,or nitrite nitrogen.While the nitrite nitrogen was used preferentially for denitrification in the mixed nitrogen sources system of nitrate nitrogen and nitrite nitrogen.Under the condition of high nitrogen concentration,the heterotrophic nitrification and aerobic denitrification of the strain were inhibited to some extent.The results provide theoretical guidance and technical support for the application of strain DW-10 in the removal of nitrogen in the complex aquaculture water environment.