Isolation And Biodegradation Characteristics Study Of Indole-Degrading Bacteria

Nitrogen Heterocyclic Compounds (NHCs) are widely exists in pollutions of many chemical industries, such as cooking, dyestuffs, pharmaceuticals, cosmetics and agrochemicals. Most of NHCs are toxic and offensive odors. Some of them are teratogenic, carcinogenic and mutagenic. If NHCs discharged in environment, it is hard to biodegradation as they are inhibiting for microorganisms. NHCs could stabilize in soil and water. It is a big threat for environment and human health.In this study, indole was as the carbon source. The indole degrading mesophiles were isolated from the facultative tank of a coking of coke wastewater wastewater treatment from a cooking plant, Sichuan. The degradation characteristics under different conditions were investigated. The nitrogenous metabolism in indole biodegradation process and degradation of other NHCs compounds by Bacillus L1 were also studies. The conclusions are as follows:1. Isolation of the indole degradation mesophiles. This strain, which could grow with indole as sole source of carbon, was isolated from facultative tank of coke wastewater treatment from a cooking plant, Sichuan. And it has high degradation efficiency to indole. It was Gram-negative, rod-shaped and grew aerobically. It could utilize glucose and showed positive test for starch hydrolysis test but negative for Voges-Prokauer test and methyl red test. It was named Bacillus L1.2. Indole degradation characteristics by Bacillus L1 were studied. When the initial indole concentration was ≤400 mg/L, the indole removal could reach more than 95.0%. With the increased of indole concentration, more time was need for microorganism growth, and the lag phase was longer. When the initial concentration was reach 450 mg/L, no significant growth of Bacillus L1 and degradation of indole. Bacillus L1 could growth when pH was 6.00～10.0, but indole was observed no significant degradation if pH≤5.00. When the temperature was ≤45℃, Bacillus L1 could growth. The suitable temperature for indole degradation and Bacillus L1 growth was 30-37℃. Bacillus L1 is a mesophiles. Glucose was added in the cultures as the external carbon source. But it seemed no significant effect for indole degradation.3. The nitrogenous metabolism in indole degradation process was studied. Nitrogen source of Bacillus L1 growth was composed of indole and (NH4)2SC2. Throughout the degradation process, some of the nitrogen from indole and (NH4)2SC2 were used for microorganism growth, and other was transform into to NC3-. When the initial indole concentration was 97.4 mg/L, the production of NO3- was 86.3 mg/L.4. The degradation efficenty of other NHCs by Bacillus L1. Indole, pyridine, quinoline, phenol and 3-methylindole (about 100 mg/L) were as target pollutants to explored degradation ability of Bacillus L1. In addition to indole, Bacillus L1 could degrade quinoline and phenol. The degradation efficiency for quinoline and phenol were reached 74.4% and 39.5%. But pyridine and 3-methylindole were almost no degradation.