Studies On The Biodegradation Of Quinoline And Methylquinolines

Quinoline and its derivatives occur widely in natural products such as coal tar, mineral oil, creosote, various fossil fuels and plants alkaloids. They are also used widely as raw materials and solvents in the manufacture of dyes, paints, fungicide, drugs, Pharmaceuticals and wood-treatment chemicals. Quinoline and its derivatives have already become common contaminants in soil and ground water, especially in the near of landfills solid wastes, as well as wood preservation and fossil fuel facilities. Many studies have shown that quinoline and its derivatives have toxic, carcinogenic and mutagenic activity to animals and humans. Researches suggest that the metabolic breakdown of quinoline and its derivatives by microorganisms is considered to be one of the major routes of environmental degradation for these widespread organic pollutants due to their low rate of photolysis. Therefore, it is beneficial to isolate high effective quinoline and its derivatives-degrading bacteria and study their degradation characteristics not only for the development of effective treatment methods for these organic pollutants but also for the understandings of their changes, transformation, fates risk assessment in the environment and the strategies for bioremediation of polluted sites.A strain Q10, which was isolated from an enrichment culture obtained from activated sludge of a gas-generating wastewater treatment plant and identified as Comamonas testosteroni, is capable of utilizing quinoline as sole source of carbon and energy. In this paper the degradation capability of the strain Q10 for quinoline and its derivatives, environmental influencing factors, the application of immobilized technology to the biodegradation of these pollutants and degradation mechanisms were studied and the conclusions are as follows:(1) Comamonas testosteroni has a broad-spectrum degradation or transformation capabilities of quinoline and its derivatives. Quinoline and 3-methylquinoline can be degraded efficiently and the strain Q10 can grow well on these two substrates. 4-methylquinoline and 6-methylquinoline can be partly removed by strain Q10 whereas no significant cell growth was observed when the two compounds were used as the substrate, respectively. Poor transformation of isoquinoline and 2-methylquinoline was observed and the strain Q10 cannot grow on them when they were used as substrate, respectively.Abstract(2) The biodegradation characteristics of quinoline and its derivatives by strain Qio were studied systemically and the results showed that environmental factors had significant effects on the biodegradation of quinoline and its derivatives. Temperature played an important role in the biodegradation of quinoline and its derivatives. The biodegradation efficiencies of quinoline and its derivatives would be decreased significantly when temperature was higher than 35 or lower than 20, respectively, and the optimum temperature was 30. The strain Q can degrade these pollutants at a wide range of pH values but weak alkaline conditions would be more beneficial to the biodegradation of quinoline and its derivatives. Oxygen demand during quinoline and its derivatives biodegradation by strain Q can be satisfied at a rotary speed of 60 r/min. The degradation efficiencies would be retarded with the increase of initial concentration of substrates, while the increase of initial cell concentration would improve the degradation efficiencies. Addition of inorganic-N source had no significant effect on the biodegradation of these substrates.(3) The substrates interactions among quinoline and its derivatives biodegradation by strain Q were studied for the first time and the results showed that the presence of quinoline had an important effects on the biodegradation of other compounds. The presence of quinoline had no apparent effects on the biodegradation of isoquinoline and 2-methylquinoline. A competitive metabolism inhibition was found when quinoline and 3-methylquinoline were used as substrates, but 3-m...