Achromobacter denitrificans strain SP1 produces an intracellular esterase upon utilizing di(2ethylhexyl)phthalate

Abstract

Production of an esterase by Achromobacter denitrificans strain SP1 – a di(2-ethylhexyl)phthalate (DEHP) degrading novel bacterium – in a modified basal salt medium supplemented with DEHP as an inducer-cum-additional carbon source was studied. The Plackett–Burman and Box–Behnken designs were applied to statistically optimize the production parameters, which resulted in an increase of esterase production by 24%. For the production of the maximum (30.5 U) intracellular esterase, 10 mM DEHP and 72 h incubation at pH 8.0 were found as optimum conditions; while the predicted value was 28.8 U with a correlation coefficient of 0.932; which signifies the fitness of the model. The optimum activity of the 2.5 folds purified esterase was 89.5 U with 20 mM para-nitrophenyl acetate as substrate (50 °C, pH 8.0 and for 30 min), and various metal ions were found to retarde the esterase activity. The approximate MW of partially purified esterase was 53 kDa, and the activity of esterase was also confirmed by native-PAGE. The Km and Vmax values of esterase were 1.308 mM and 62.52 μmol min−1 mg−1, respectively. Briefly, this was the first report on an enzyme from the DEHP degrading A. denitrificans SP1, which in comparison with esterase from other phthalate degrading bacteria and fungi showed better Km and Vmax.