Biodegradation of Dimethyl Phthalate, Diethyl Phthalate, Dibutyl Phthalate and Their Mixture by VariovoraxSp

Abstract

Biodegradation of dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) and their mixture by a bacterial strain is reported. The strain was isolated by enrichment technique from garbage dumped soil nearby Indian Institute of Technology Bombay. The isolate had the ability to utilize mixture of DMP, DEP and DBP in the growth medium as well as the individual phthalate esters as the sole source of carbon and energy. The bacterial isolate was identified as Variovorax sp. based on 16S r-DNA sequence analysis. Variovorax sp. degraded >99% of 300 mg/l of DMP, DEP, DBP or a mixture containing 100 mg/l of each within 30 h. Metabolites or end products were not detected by HPLC 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 the order: DEP>DMP>DBP. Crude cell free extracts prepared from bacterial isolates contained cocktail of inducible enzymes responsible for the degradation of DMP or DEP.