Abstract

Chloroaromatic pollutants from bleached Kraft pulp mill effluents (BKME) are difficult to degrade, because bacterial strains present in BKME aerobic treatments, only partially degrade these compounds, accumulating the corresponding chlorocatechol intermediates. To improve the catabolic performance of chlorocatechol-accumulating strains, we introduced, by chromosomal insertion, the tfdI CDEF gene cluster from Ralstonia eutropha JMP134 (pJP4). This gene cluster allows dechlorination and channelling of chlorocatechols into the intermediate metabolism. Two bacterial strains, R. eutropha JMP222 and Pseudomonas putida KT2442, able to produce chlorocatechols from 3-chlorobenzoate (3-CB) were used. Acinetobacter lwoffii RB2 isolated from BKME by its ability to grow on guaiacol as sole carbon source and shown to be able to produce the corresponding chlorocatechols from the BKME pollutants 4-, and 5-chloroguaiacol, was also used. The tfdI CDEF gene cluster was inserted in the chromosome of these strains using miniTn5-derived vectors that allow expression of the Tfd enzymes driven by the lacIq/Ptrc or tfdR/Ptfd-I regulatory systems, and therefore, responding to the inducers isopropyl-