Transformation of mono- and dichlorinated phenoxybenzoates by phenoxybenzoate-dioxygenase inPseudomonas pseudoalcaligenes POB310 and a modified diarylether-metabolizing bacterium

Pseudomonas pseudoalcaligenes POB310 contains genes that encode phenoxybenzoate dioxygenase. The enzyme transforms mono- and dichlorinated phenoxybenzoates to yield protocatechuate that is used as a growth substrate and chlorophenols that are nonmetabolizable. Mass spectral analysis of 18O metabolites obtained from the protocatechuate 3,4-dioxygenase-deficient mutant, POB310-B1, suggested that the reaction mechanism is a regioselective angular dioxygenation. A cloning vector containing reaction relevant genes (pD30.9) was transferred into Pseudomonas sp. strain B13 containing a modified ortho-cleavage pathway for aromatic compounds. The resultant Pseudomonas sp. strain B13-D5 (pD30.9) completely metabolized 3-(4-chlorophenoxy)benzoate. During growth on 3-phenoxybenzoate, strain B13-D5 (pD30.9) (Ks = 0.70 ± 0.04 mM, μmax = 0.45 ± 0.03 h−1, td = 1.5 h, Y = 0.45 ± 0.03 g bio- mass · g substrate−1) was better adapted to low substrate concentrations, had a faster rate of growth, and a greater yield than POB310 (Ks = 1.13 ± 0.06 mM, μmax = 0.31 ± 0.02 h−1, td = 2.2 h, Y = 0.39 ± 0.02 g biomass · g substrate−1).