Hydrolytic dehalogenation of the chlorothalonil isomer o-tetrachlorophthalonitrile by Pseudochrobactrum sp. BSQ-1

Abstract Microbial dehalogenation plays key roles in the biodegradation and detoxification of halogenated aromatics. Although the hydrolytic dehalogenation of halogenated aliphatic hydrocarbons and carboxylic acids has been extensively studied, there are few reports on the hydrolytic dehalogenation of halogenated aromatics. In this study, the aerobic strain BSQ-1, isolated from soils contaminated with halogenated aromatics in Jiangsu, China, was able to completely degrade 0.12 mM o -tetrachlorophthalonitrile in 84 h in the presence of 2 mM sodium acetate trihydrate and released one equivalent of chlorine ions. MS–MS and NMR analysis revealed that o -tetrachlorophthalonitrile was dehalogenated to 4-hydroxyl- o -trichlorophthalonitrile. The dehalogenation of o -tetrachlorophthalonitrile could occur under both aerobic and anaerobic conditions, showing that the observed dehalogenation was a hydrolytic process. The optimal temperature and pH for o -tetrachlorophthalonitrile dehalogenation by strain BSQ-1 were 30 °C and 8, respectively. It was found that 0.2 mM Zn 2+ , Mg 2+ or Co 2+ enhanced dehalogenation activity, whereas 0.2 mM Fe 3+ , Ni 2+ , Cu 2+ , Ca 2+ , or Pb 2+ inhibited dehalogenation activity. Strain BSQ-1 was able to dehalogenate not only o -tetrachlorophthalonitrile but also its two isomers, chlorothalonil and p -tetrachlorophthalonitrile. This study presents a new example of the hydrolytic dehalogenation of halogenated aromatics by microorganisms and provides a good candidate strain for the clean-up of tetrachlorophthalonitrile-contaminated sites.