Current insights into the microbial degradation for butachlor: strains, metabolic pathways, and molecular mechanisms.

The herbicide butachlor has been used in huge quantities worldwide, affecting various environmental systems. Butachlor residues have been detected in soil, water, and organisms, and have been shown to be toxic to these non-target organisms. This paper briefly summarizes the toxic effects of butachlor on aquatic and terrestrial animals, including humans, and proposes the necessity of its removal from the environment. Due to long-term exposure, some animals, plants, and microorganisms have developed resistance toward butachlor, indicating that the toxicity of this herbicide can be reduced. Furthermore, we can consider removing butachlor residues from the environment by using such butachlor-resistant organisms. In particular, microbial degradation methods have attracted much attention, with about 30 kinds of butachlor-degrading microorganisms have been found, such as Fusarium solani, Novosphingobium chloroacetimidivorans, Chaetomium globosum, Pseudomonas putida, Sphingomonas chloroacetimidivorans, and Rhodococcus sp. The metabolites and degradation pathways of butachlor have been investigated. In addition, enzymes associated with butachlor degradation have been identified, including CndC1 (ferredoxin), Red1 (reductase), FdX1 (ferredoxin), FdX2 (ferredoxin), Dbo (debutoxylase), and catechol 1,2 dioxygenase. However, few reviews have focused on the microbial degradation and molecular mechanisms of butachlor. This review explores the biochemical pathways and molecular mechanisms of butachlor biodegradation in depth in order to provide new ideas for repairing butachlor-contaminated environments. KEY POINTS: • Biodegradation is a powerful tool for the removal of butachlor. • Dechlorination plays a key role in the degradation of butachlor. • Possible biochemical pathways of butachlor in the environment are described.