Characterization of 2,4-Dichlorophenoxyacetic Acid Degrading Bacteria Harboring α- Ketoglutarate Dioxgenase Enzyme

Abstract

2,4-dichlorophenoxyacetic acid/α-ketoglutarate dioxygenase is the first enzyme in the catabolic pathway for the herbicide 2,4-dichlorophenoxyacetic acid. In this study, these enzymes were inducible and the serial adaptation
of four studied bacterial isolates steadily evolved strains, which exhibited higher, and significantly different rates of 2,4-dichlorophenoxyacetic acid metabolism. For biomass production relative to the original starting strain 2,4-dichlorophenoxyacetic acid/α-ketoglutarate dioxygenase was partially purified to apparent homogeneity from four bacterial isolates that were studied, using ammonium sulphate precipitation and gel filtration on sephadex G-100. 2,4-dichlorophenoxyacetic acid concentration resulted in a lower yield of the cell biomass of the in vitro culture of each of the bacterial isolates and consequently a lower enzyme yield. There was a gradual increase in enzyme activity from the different bacterial isolates at pH 5.5, maximum enzymes activity at pH 7.5 and no activity at pH 10.0. Optimum temperature for enzyme activity was at 35 o C but activity was reduced to zero at 60 o C. Conclusively, the four studied bacterial isolates and their cell-free extracts may be applicable for 2,4-dichlorophenoxyacetic acid assimilation and bioremediation in 2,4-dichlorophenoxyacetic acid contaminated environment.