Process optimization and kinetic study of biodegradation of dimethyl phthalate by KS2, a novel strain of Micrococcus sp.

The present study elucidates identification and characterization of dimethyl phthalate (DMP) degrading novel bacterial strain, Micrococcus sp. KS2, isolated from soil contaminated with municipal wastewater. Statistical designs were exercised to achieve optimum values of process parameters for DMP degradation by Micrococcus sp. KS2. The screening of the ten important parameters was performed by applying Plackett-Burman design, and it delivered three significant factors (pH, temperature, and DMP concentration). Further, response surface methodology involving central composite design (CCD) was implemented to examine mutual interactions among variables and achieve their optimal response. The predicted response indicated that maximum DMP degradation (99.67%) could be attained at pH 7.05, temperature 31.5 °C and DMP 289.19 mg/l. The strain KS2 was capable of degrading up to 1250 mg/l of DMP in batch mode and it was observed that oxygen was limiting factor in the DMP degradation. Kinetic modeling of DMP biodegradation indicated that Haldane model fitted well with the experimental data. During DMP degradation, monomethyl phthalate (MMP) and phthalic acid (PA) were identified as degradation metabolites. This study provides insight into DMP biodegradation process and proposes that Micrococcus sp. KS2 is a potential bacterial candidate to treat effluent containing DMP.