Isolation And Screening Of Dimethylformamide Biodegrading Bacteriaand Study On It's Degradation Pathway

N,N-dimethylformamid (DMF) is widely used as solvent or main chemical raw materials in various industries. DMF have acertain toxicity to humans and animals. So emissions of industrial waste water containing DMF will cause serious harm to the environment.Both at home and abroad, in the treatment methods of wastewater containing DMF (included physico-chemical method, chemical method and biological methods), using biological methods can reduce cost, and products of degradation are non-toxic, so biological methods is suit to treatment a number of wastewater containing DMF. Due to DMF have a poor biochemical quality, and also have toxicity to degrading bacteria, so DMF will affect the degradation rate of biological wastewater treatment process. In order to improve the effectiveness of wastewater treatment process, the premise must be obtain high efficiency degrading bacteria, it can be seen that high efficiency degrading bacteria, which isolation and screen from environment, is particularly important.In this study, the degrading bacteria was isolated from an enrichment culture developed using activated sludge from water treatment unit as the source inoculums, and through morphology, physiological and biochemical characteristics and molecular biology of strains to identified the isolated bacteria. In order to understand the growth and degradation of isolated bacteria in a different environment, further study on the growth and degradation characteristics of bacteria. Through the utilization of the middle products by strains, as well as the intermediate product which product in the degradation produces, determine biodegradation pathway of strains. At the same time, using the way of ultraviolet mutagenesis, to obtain some strains which one have a better degrading efficiency.The mainly results of this study are as follows:(1) Two strains capable of utilizing DMF as its sole carbon and nitrogen was isolated from batch culture enrichments of activated sludge. The two isolated strains belong to the strains of Paracoccus sp . In the medium containing DMF concentration of 0.5%, two isolated strains can degrade 75%⁸0% of DMF after 48h.(2) In certain DMF concentration range, proper reduce pH value of the bacterium growth environment, will be helpful for the growth and degradation of two strains in the late culture stage. Meanwhile, two strains of bacteria could tolerate very high concentrations of DMF as the growth was observed even at 5%. (3) The kinetic constants of DMF3 wereμ_max=0.22129h-1, K_s=0.4108g/L, K_i=25.92735g/L; so the kinetic equation as follows:(4) The biodegradation of DMF proceeds by two strains are as follows: N,N-dimethylformamidase(DMFase) will converts DMF to dimethylamine (DMA) and formate. These two catabolic intermediates are further degraded to form ammonia and carbon dioxide by following the known metabolic pathway that is typically found in a number of methylotrophs.(5) By the way of ultraviolet mutagenesis, obtained two strains with a better degradation than isolated strains, its degradation effect than the original strains raised about 14.8%å’Œ19.4%, respectively.