Complete degradation of dimethyl phthalate by a Comamonas testosterone strain.

A Comamonas testosterone bacterial strain, named as DB-7, capable of utilizing dimethyl phthalate (DMP) as sole carbon source and energy for growth was isolated from soil with plastic film mulching by an enrichment culture technique. This bacterium was identified as C. testosterone by 16S rRNA sequence analysis and phospholipid fatty acid profile. DB-7 could degrade more than 99% of 450 mg L-1 DMP within 14 hours, and degraded DMP of different concentrations rapidly. The optimal degradation temperature and pH were 30-35 °C and pH 9.0, respectively. The degradation rate of DMP was positively related to inoculum volume of the bacterium. The result of HPLC and LC/MS analysis of metabolic products indicated that the major degrading intermediates were mono-methyl phthalate (MMP) and phthalic acid (PA) during the degradation of DMP by DB-7. Partial sequences of three genes involved in PA metabolism were detected in DB-7, and the expression of phthalate 4, 5-dioxygenase was drastically induced in the presence of DMP and PA. DB-7 is promising to be applied to DMP bioremediation because of its high degrading efficiency.