Biodegradation of dimethyl phthalate ester using free cells, entrapped cells of Variovorax sp. BS1 and cell free enzyme extracts: A comparative study

• DMP was biodegraded by free and alginate entrapped cells of Variovorax sp.
• Isolated strain was efficient in biodegrading wide range of concentrations of DMP.
• Entrapped cells re-used 10 times for batch biodegradation of DMP in plain water.
• Biodegradation of DMP, DEP, DBP observed with cell free enzymes of Variovorax sp.
• Phthalic acid observed during enzymatic DMP biodegradation in the presence of Zn+2.

Whole cells of Variovorax sp. BS1 had the ability to biodegrade up to 600 mg L−1 (3.08 mM) of dimethyl phthalate (DMP) at the end of 30 h of incubation at 30 °C. The total organic carbon analyses suggested mineralization of DMP using isolated bacterial strain. The cell-free extracts of Variovorax sp. BS1 contained mixture of enzymes required for the complete biodegradation of DMP, diethyl phthalate (DEP) and dibutyl phthalate (DBP). Transient intermediates or end products were not detected by HPLC and LC-MS analyses during or after biodegradation of DMP by Variovorax sp. BS1. Addition of Zn+2 to assay mixture containing DMP and cell free extract resulted in the accumulation of detectable quantity of metabolite, ortho-phthalate thereby suggesting that DMP biodegradation proceeded via de-esterification reactions. Cells of Variovorax sp. BS1 entrapped in calcium alginate beads could be re-used for atleast ten sequential cycles in plain water with diminutive loss of DMP biodegradation activity. Results suggested that whole cells, alginate entrapped cells of Variovorax sp BS1 and enzymes present in the cell free extracts may be used for efficient biodegradation of dimethyl phthalate.

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