Degradation of the endocrine - disrupting dimethyl phthalate and dimethyl isophthalate by mangrove microorganisms

摘要

Degradation of ortho-dimethyl phthalate (o-DMP) and dimethyl isophthalate (DMI) was investigated using microorganisms isolated from mangrove sediment in Hong Kong. One enrichment culture was capable of utilizing o-DMP as the sole source of carbon and energy, but none of the bacteria in the enrichment culture was capable of degrading o-DMP alone. In co-culture of two bacteria, degradation was observed and one bacterium in the culture was a new species unkown before. Biochemical utilization profile of this bacterium is limited to malate, acetate and phenyl acetate only. Complete degradation of o-DMP took place in less than 4 days at 400 mg/L. Degradation proceeds through monomethyl phthalate ester and phthalic acid before the aro-matice ring opening. Using DMI as the sole carbon and energy source, Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr were isolated for enrichment culture. DMI was found to be degraded through the biochemical cooperation between the two species and the initial hydrolytic reaction of the ester bond by K. oxytoca Sc and the next step of transformation was by M. mesophilicum Sr, and IPA was degraded by both of them. Our data suggest that the plasticizer phthalate esters can be mineralized by consortia of bacteria and biochemical cooperation between bacteria plays an important role in the ecological community of the natural environment.