Achromobacter xylosoxidans bacteria isolated from contaminated agricultural environment for a sustainable 2,4-dichlorophenoxyacetic acid herbicide degradation: An experimental study

In the agricultural sector, a class of chemical compounds known as chlorinated phenol and phenoxyacetic acid are employed as herbicides, wood preservatives, and pesticides. Certain groups of chlorinated phenoxyacetic acid are used as herbicides for agricultural and domestic application. They are listed as priority pollutants by the United States Environmental Protection Agency (USEPA). Thus, this study focuses on bacterial isolation for 2,4-dichlorophenoxyacetic acid herbicide degradation been a toxic contaminant that hinders the quality of the soil over time, availability of certain soil microbes, non-targeted plants and poses health risk even to humans such as Hodking's lymphoma, respiratory infections e.t.c. These therefore, make it necessary to search for scientific way of dealing with this chemical from our environments. Incubation time, substrate concentration, pH, temperature, and inoculum size in mineral salt medium were all the parameters tested during the study, while 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide was used as the alternative source of carbon. Following systemic dilution of sample on mineral salt medium, three bacterial isolates (D1, D2, and D3), were isolated and subjected to lots of screening. D2 was proven to be the best. During molecular identification that involves polymerase chain reaction, gel electrophoresis, sequence alignment and phylogentic analysis, the isolated bacteria was found to be Achromobacter xylosoxidans. The bacterial isolate grew and degraded 2,4-dichlorophenoxyacetic acid herbicide at optimum conditions of 96 h incubation time, 0.72g L−1 substrate concentration, 7.5 pH, 40 °C temperature, and 400 μg/L inoculum size. High Performance Liquid Chromatography (HPLC) analysis of the residual 2,4-dichlorophenoxyacetic acid herbicide and the standard solution probe of the isolate was able to degrade up to 95.38 % of the substrate indicating great potentiality in bioremediation of herbicide polluted environments thereby, reducing if not all eliminating these toxic contaminants from our surroundings.