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

Pseudomonas pseudoalcaligenes POB310 contains genes that encode phenoxybenz oate dioxygenase. The enzyme transforms mono- and dichlorinated phenoxybenz oates to yield protocatechuate that is used as a growth substrate and chlor ophenols that are nonmetabolizable. Mass spectral analysis of O-18 metaboli tes obtained from the protocatechuate 3,4-dioxygenase-deficient mutant, POB 310-B1, suggested that the reaction mechanism is a regioselective angular d ioxygenation. 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 so. str ain B13-D5 (pD30.9) completely metabolized 3-(4-chlorophenoxy)benzoate. Dur ing growth on 3-phenoxy-benzoate, strain B13-D5 (pD30.9) (K-s = 0.70 +/- 0. 04 mM, mu(max) = 0.45 +/- 0.03 h(-1), t(d) = 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 (K-s = 1.13 /- 0.06 mM, mu(max) = 0.31 +/- 0.02 h(-1), t(d) = 2.2 h, Y = 0.39 +/- 0.02 g biomass . g substrate(-1)). (C) 2000 John Wiley & Sons, Inc.