Characterization of a novel melamine-degrading bacterium isolated from a melamine-manufacturing factory in China

摘要

Melamine (2,4,6-triamino-1,3,5-triazine, C_3H_6N_6), belonging to the s -triazine family, is an anthropogenic and versatile raw material for a large number of consumer products and its extensive use has resulted in the contamination of melamine in the environment. A novel melamine-degrading bacterium strain CY1 was isolated from a melaminemanufacturing factory in China. The strain is phylogenetically different from the known melamine-degrading bacteria. Approximately, 94 % melamine (initial melamine concentration 4.0 mM, initial cell OD 0.05) was degraded in 10 days without the addition of additional carbon source. Highperformance liquid chromatography showed the production of degradation intermediates including ammeline, ammelide, cyanuric acid, biuret, and urea. Kinetic simulation analysis indicated that transformation of urea into ammonia was the rate-limiting step for the degradation process. The melamine– cyanurate complex was formed due to self-assembly of melamine and cyanuric acid during the degradation. The tracking experiment using CY1 cells and ~(13)C_3-melamine showed that the CY1 could mineralize s -triazine ring carbon to CO_2. The strain CY1 could also catalyze partial transformation of cyromazine, a cyclopropyl derivative of melamine, to 6-(cyclopropylamino)-[1,3,5]triazine-2,4-diol.