Isolation And Cultivation Of Nitrite-Degrading Microorganism And Its Degrading Characterization

Nitrite can induce animal acute poisoning. It can also induce animal cancer as the form of nitrosamine,which comes from the combination of nitrite with a mine .Our aim in this paper is to isolate nitrobacteria that can effectively degrade nitrite and may be used in clinical tirals including the degradation of nitrite in water body and animal food.Nitrobacteria are one of the important group beneficial bacteria in soil. They can be used as food additive since they can degrade nitrite. Nitrobacter is a kind of autotroph so that grows very slowly. It forms clone after about one-week' cultivation. Aeration has not effect on the growth of bacteria .The growth curve of Nitrobacter is different from other bacteria .It enters into the period of logarithm growth after 140 hours'cultivation.Cultivated on the selective culture medium, six strains of nibrobacter, which can use nitrite as its soly nitrogen source, were screened from the soils and water from nan jing.The physiological and biochemical istics, such as salt tolerance and antibiotic resistance were tested.AIl Strains were rods and no spores.The Gram-reaction of strains were negative. The ability of degrading nitrite by these strains were compared and it was found that strain J2 had higher ability of nitrite degrading. The content of nitrite were degraded by 40.1%.Another serie of six strains including four bacteria and two fungi were isolated by enrichment cultivation. One of the germ,can use nitrite as its soly nitrogen source,namely S1, was identified P,fluorescens. Auxanography was employed to study its carbon & nitrogen source.The results showed that S1 could use most of the common carbon source as well as nitrogen source with glycerin and NaNO₂ of the optimal carbon source and nitrogen source respectively .S1 showed the highest degrading efficiency to nitrite, under the following conditions: the age of cultivating 30hrs, the inocla quantity of 10%, pH value of 7.2, temperature of 30℃, rotation speed of the shaker of 150r/min and the ratio of volume of medium and flask of 1/5.The growth of S1 was little influenced by many metal ions,such as Ba²⁺,Zn²⁺,Cu²⁺ and Al³⁺,slightly inbihited by Co²⁺,Cd²⁺ and Cr³⁺,and heavilyinhibited by Pb²⁺ and Ag+.