Biodegradation of Phenoxyacetic Acid Herbicides (MCPA AND 2,4-D) by Escherichia Coil: Insights from HPLC Detection

The present study investigates the herbicide degradation potential of Escherichia coli strain LKDA3 under varying concentrations of two commonly used phenoxyacetic herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA). Strain LKDA3, previously isolated using 500mg/L herbicide, was evaluated for its degradation efficiency at 300, 500, and 700mg/L concentrations over a 5-day incubation period in minimal salt medium supplemented with 0.2% glucose at 30 °C. Residual herbicide concentrations were quantified using high-performance liquid chromatography (HPLC), and degradation efficiency was determined by comparing chromatographic peak areas to those of untreated controls. The strain achieved complete (100%) degradation of 2,4-D at 300 mg/L, 99% at 500 mg/L, and 38.2% at 700 mg/L. A similar pattern was observed with MCPA, with ~99% degradation recorded across all concentrations. However, growth kinetics, measured via OD₆₀₀, showed concentration-dependent inhibition, particularly at 700 mg/L. Notably, MCPA induced a stronger inhibitory effect on bacterial growth compared to 2,4-D, despite high degradation efficiency. These results suggest that E. coli LKDA3 is capable of metabolizing both herbicides effectively, although elevated concentrations exert growth-limiting effects. The findings highlight the potential application of LKDA3 in bioremediation strategies targeting phenoxy herbicide-contaminated environments.