Investigation of the biodegradability of pendimethalin by Bacillus subtilis, Pseudomonas fluorescens, and Escherichia coli

Pendimethalin is a persistent herbicide. It is the third most widely used selective herbicide applied in soil that negatively affects humans and the environment. The current experiment assessed the ability of three bacterial species to degrade this herbicide. Pendimethalin was added to flasks in a 125 mg/L concentration and 107 CFU.mL-1 of Bacillus subtilis, Pseudomonas fluorescens, and Escherichia coli were added separately to the mineral salts medium media (MSM) and stored on a rotary shaker. The bacterial cell number, wet biomass, and chemical oxygen demand (COD) were determined after seven days. The concentration of pendimethalin residue was then determined using high-performance liquid chromatography (HPLC). A completely randomized design (CRD) with three replicates was used to arrange the experimental units, except for HPLC with only one replicate. The experimental results showed that all three bacterial growths rose after seven days post-inoculation in the pendimethalin modified media. A comparison of the growth kinetics of bacteria in the herbicide modified media and the control showed that the bacteria grew faster in the presence of the herbicide. The reduction in the COD parameter occurred in all the tested bacteria, but the highest COD removal efficiency (85%) was observed with B. subtilis. The highest biological degradation of pendimethalin compared to the control occurred in the B. subtilis inoculated media (78%), which also produce the most cell density. Based on the HPLC results, all three bacterial species were capable of biodegrading pendimethalin herbicide, with B. subtilis as the most effective bacterium, followed by E. coli and P. fluorescens.