Kinetic modeling and metabolite identification of dimethyl phthalate biodegradation by Bacillus sp KS1 isolated from municipal wastewater contaminated soil

Phthalate esters (PEs) have engrossed attention and intensified environmental concern owing to their widespread applications. In the present study, dimethyl phthalate (DMP), a low molecular weight PE, degrading aerobic bacterium was isolated from soil contaminated with municipal wastewater. Based on morphological, biochemical characteristics and 16S rRNA sequencing, the isolate was identified as Bacillus sp. KS1. Complete degradation up to 1,400 mg/L of DMP was observed within 168 h. At low concentrations (25-100 mg/L) of DMP, degradation data fitted well with the first-order kinetics, and the half-life was observed as 3 h. Growth kinetic study of the high concentrations of DMP (0-1,400 mg/L) was performed by using various kinetic models where Haldane model was found to fit well with the experimental data (R-2 = 0.9210). Analysis of DMP degradation residual by high-performance liquid chromatography and electrospray ionization-mass spectrometry revealed the presence of phthalic acid as the DMP degradation metabolite. The results obtained in the present study will be significant for exploring an application of Bacillus sp. KS1 for bioremediation of PEs.