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

Melamine (2,4,6-triamino-1,3,5-triazine, C₃H₆N₆), 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 melamine-manufacturing 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. High-performance 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 ¹³C₃-melamine showed that the CY1 could mineralize s-triazine ring carbon to CO₂. 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.