Bacilli- Mediated Degradation of Xenobiotic Compounds and Heavy Metals

Abstract

Xenobiotic compounds are man-made compounds and widely used in dyes, drugs, pesticides, herbicides, insecticides, explosives, and other industrial chemicals. These compounds have been released into our soil and water due to anthropogenic activities and improper waste disposal practices and cause serious damage to aquatic and terrestrial ecosystems due to their toxic nature. The United States Environmental Protection Agency (USEPA) has listed several toxic substances as priority pollutants. Bacterial remediation is identified as an emerging technique to remove these substances from the environment. Many bacterial genera are actively involved in the degradation of toxic substances. Among the bacterial genera, the members of the genus Bacillus have a great potential to degrade or transform various toxic substances. Many Bacilli have been isolated and characterized by their ability to degrade or transform a wide range of compounds including both naturally occurring substances and xenobiotic compounds. This review describes the biodegradation potentials of Bacilli toward various toxic substances, including 4-chloro-2-nitrophenol, insecticides, pesticides, herbicides, explosives, drugs, polycyclic aromatic compounds, heavy metals, azo dyes, and aromatic acids. Besides, the advanced technologies used for bioremediation of environmental pollutants using Bacilli are also briefly described. This review will increase our understanding of Bacilli-mediated degradation of xenobiotic compounds and heavy metals.

Keywords: 4-Chloro-2-nitrophenol; Bacillus; cypermethrin; ibuprofen; naproxen; polycyclic aromatic hydrocarbons.

Figure 1

Biotransformation pathway of 4-chloro-2-nitrophenol in Bacillus spp. (Arora, 2012).

Figure 2

A degradation pathway of naphthalene in Bacillus fusiformis strain BFN (Lin et al., 2010).

Figure 3

Degradation pathways of anthracene by Bacillus licheniformis MTCC 5514 (Swaathy et al., 2014).

Figure 4

Degradation pathways of cypermethrin in Bacillus sp. SG2 and Bacillus subtilis BSF01 (Xiao et al., ; Pankaj et al., 2016).

Figure 5

Degradation pathways of cypermethrin in Bacillus subtilis strain 1D (adapted from Gangola et al., 2018).

Figure 6

Degradation pathway of cyhalothrin in Bacillus thuringiensis ZS-19 (adapted from Chen et al., 2015).

Figure 7

Degradation pathway of fenpropathrin in Bacillus sp. DG-02 (Reprinted (adapted) from Chen et al., 2014). Copyright (2014) American Chemical Society.

Figure 8

Degradation pathway of ibuprofen in Bacillus thuringiensis B1 (adapted from Marchlewicz et al., 2017).

Figure 9

Degradation pathway of naproxen in Bacillus thuringiensis B1 (Górny et al., 2019).