EXPRESSION AND SUBSTRATE-SPECIFICITY OF THE TOLUENE DIOXYGENASE OF PSEUDOMONAS-PUTIDA NCIMB-11767

Pseudomonas putida NCIMB 11767 oxidized phenol monochlorophenols, seve ral dichlorophenols and a range of alkylbenzenes (C-1-C-6) via an indu cible toluene dioxygenase enzyme system. Biphenyl and naphthalene were also oxidized by this enzyme. Growth on toluene and phenol induced th e meta-ring-fission enzyme, catechol 2,3-oxygenase, whereas growth on benzoate, which did not require expression of toluene dioxygenase, ind uced the ortho-ring-cleavage enzyme, catechol 1,2-oxygenase. Monochlor obenzoate isomers and 2,3,5-trichlorophenol were gratuitous inducers o f toluene dioxygenase, whereas 3,4-dichlorophenol was a fortuitous oxi dation substrate of the enzyme. The organism also grew on 2,4- and 2,5 -dichloro isomers of both phenol and benzoate, on 2,3,4-trichloropheno l and on 1-phenylheptane. During growth on toluene in nitrogen-limited chemostat culture, expression of both toluene dioxygenase and catecho l 2,3-oxygenase was positively correlated with increase in specific gr owth rate (0.11-0.74 h(-1)), whereas the biomass yield coefficient dec reased. At optimal dilution rates, the predicted performance of a 1-m( 3) bioreactor supplied with Ig nitrogen 1(-1) for removal of toluene w as 57 g day(-1) and for removal of trichloroethylene was 3.4 g day(-1) . The work highlights the oxidative versatility of this bacterium with respect to substituted hydrocarbons and shows how growth rate influen ces the production of competent cells for potential use as bioremediat ion catalysts.