Biodegradation of Phthalate Esters by Variovorax sp

Biodegradation of dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) and their mixture by a bacterial strain that was isolated from garbage dumped soil nearby Indian Institute of Technology Bombay is reported. The strain was isolated by enrichment technique using a mixture of DMP, DEP and DBP in the growth medium and had the ability to utilize the above phthalate esters as the sole source of carbon and energy under aerobic conditions. The bacterial isolate was identified as Variovorax sp. based on 16S r-DNA sequence analysis. Variovorax sp. degraded >99% of 300 mg L-1 of DMP, DEP, DBP or a mixture containing 100 mg L-1 of each within 30 h. Metabolites were not detected by HPLC or LC-MS analyses. Biodegradation of phthalate esters followed first-order kinetics. The rates of biodegradation of individual esters followed the order DEP>DBP>DMP while in the mixture, rates followed DEP>DMP>DBP. Results obtained suggested that the isolated Variovorax species was highly efficient in biodegrading DMP, DEP, DBP or their mixture.