Aerobic biodegradation and optimization of 2,4-Dichlorophenoxyacetic acid by E. hormaechei subsp. Xiangfangensis and assessment of biodegraded metabolite toxicity

Abstract

Nature has its hidden battalion against all the manmade environmental contaminations. Ethno-medicinal plants and their hidden microbiome are the natural treasures that are in need to be explored The present work is focused on isolating the endophytic bacteria of Annona reticulata, Cinnamomum zeylanicum and Gloriosa superba Isolated bacterial strains are screened for the potential degrader of 2,4-D depending on their efficiency to tolerate a higher mg L−1 of 2,4-D. Enterobacter hormaechei Subsp. xiangfangensis strain 19_357_F (MK281611), isolated from the bark explant was capable of co-existing and utilizing 2,4-D as a source of nourishment, thus degrading 2,4-D to 2,4-DCP. The optimization of biodegradation was carried out using one factor at a time (OFAT) approach and the isolated strain could tolerate 400 mg L−1 of 2,4-D while degrading 250 mg L−1 of dye accounting for 42.68% degradation at 72 h. The present study indicates the endophyte Enterobacter hormaechei subsp. xiangfangensis strain 19_357_F capable of utilizing 2,4-D as the sole source of energy, on further increasing the 2,4-D above 400 mg L−1 the bacterial toxicity was induced demonstrating the reduction in the bacterial cell count The current study also reported the biodegraded metabolite 2,4-DCP more toxic than the parent compound and suggestive of increasing the time of incubation. The endophyte Enterobacter hormaechei subsp. xiangfangensis strain 19_357_F is considered efficient as it can degrade 2,4-D at 250 mg L−1 with 42.68% quantitatively. The aim of the study is to explore these potential organisms as tool for bioremediation and enhance the environmental self-sustainability as these endophytes are safer, reliable, non-pathogenic and eco-friendly.