An attempt to control the polychlorocatechol pigment production during 3-chlorobenzoate aerobic co-metabolism in growing-cell batch culture.

A strain of Pseudomonas fluorescens, designed CP30, was capable of co-metabolizing 3-chlorobenzoic acid via chlorocatechols, thus producing a polychlorocatechol black pigment. The pigment production was found to be enzyme-mediated in P. fluorescens cultures; however, the results of the autoxidation studies suggested that a large amount of pigment could derive from the simple autoxidation of the chlorocatechols accumulated in the CP30 culture during the 3-chlorobenzoate degradation. The polymerization of chlorocatechols should reduce the toxicity of the culture and generally resulted in a large production of a water-insoluble (i.e. a easily removable) pigment with the release a large amount of chloride ions. Both 3-chlorobenzoate degradation and pigment production were stimulated and inhibited in the same way by high and low pH values, respectively, in CP30 cultures; the culture conditions which permitted an extensive 3-chlorobenzoate degradation with the lowest pigment production were not identified. However, on the basis of the detoxification property of the pigment production process, high pH and dissolved oxygen concentrations appears to be the most suitable culture conditions for an enhanced detoxicant treatment of 3-clorobenzoate-contaminated waste water.