The bacterial biotransformation of the biocide IPBC, widely used as an antisapstain wood preservative, was investigated in bacteria isolated from failed wood, soil experiencing IPBC wash-off, and John Innes No. 2 compost. Nine strains of bacteria were isolated, belonging to the genera Alcaligenes, Enterobacter, Microbacterium and Pseudomonas. The sole organic degradation product in an enteric bacterium ‘W1’, isolated from failed wood, was PBC, which was produced at 1:1 stoichiometry. No further degradation products were isolated: PBC appeared to be the terminal product of transformation. Incubation of 0.8 mM IPBC in mineral medium with W1 for 90 hr caused the IPBC concentration to fall to undetectable levels, and the toxicity of spent broth was reduced to zero for four target fungi as measured by an antibiotic assay disc bioassay. Furthermore, the toxicity of PBC to the fungi as bioassayed, was c. 1/1000 that of IPBC. The widespread ability of common soil and wood bacteria to transform IPBC to less toxic products is an important contribution to an understanding the environmental fate of IPBC and its continued use under the auspices of the European Biocidal Products Directive (BPD).

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