A Pandoraea sp. strain efficiently degrades chlorobenzene via monooxygenation pathways with high potential for groundwater bioremediation

Chlorobenzene (CB) is often detected in contaminated soil and groundwater at in-service petrochemical facilities. Given the high safety requirements for these petrochemical facilities, a sustainable and low-consumption microbial remediation technology is preferred. The aim of this study was to isolate an efficient chlorobenzene-degrading bacterial strain and understand its degradation mechanism to be used for in-situ bioremediation of chlorobenzene-contaminated sites in in-service petrochemical enterprises. A degrading bacterium was isolated from chlorobenzene-contaminated soil at a pesticide plant, identified as Pandoraea sp. XJJ-1 (CCTCC M 2021057). This strain completely degraded 100 mg·L ^− 1 CB and showed extensive degradability across a range of pH (5.0–9.0), temperature (10°C-37°C), and CB concentrations (100–600 mg·L ^− 1 ). Notably, the degradation efficiency was 85.2% at 15°C, and the strain could also degrade six other aromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylene ( o-, m-, p- ). The metabolic pathway of chlorobenzene was inferred using Ultra Performance Liquid Chromatography (UPLC), Gas chromatography-mass spectrometry (GC-MS), and genomic analysis. In strain XJJ-1, CB was metabolized to o-chlorophenol and 3-chloroxychol by chlorobenzene monooxygenase, followed by ortho- cleavage by the action of 3-chlorocatechol 1,2-dioxygenase. This is the first report of chlorobenzene monooxygenase as the rate-limiting step in Pandoraea spp.. Strain XJJ-1, which exhibits excellent degradation ability for CB at low temperatures, was isolated in this study. Moreover, the presence of the chlorobenzene monooxygenation pathway metabolism in strain XJJ-1 is reported for the first time in Pandoraea . As a biomaterial with low temperature resistance and composite pollutant degradation capacity, strain XJJ-1 has potential applications prospects in the in-situ bioremediation of chlorobenzene-contaminated sites.