Biodegradation of dehydroabietic acid by Bacillus psychrophilus
The Saguenay River (Quebec, Canada) is situated in an industrialized area (aluminium smelters, papers mills) and receives a great amount of industrial wastewaters. Concentrations of dissolved organic matter and suspended cellulose fibers from the 4 local paper mills are relatively high in the waters of the Saguenay River and are evaluated at 29 000 tons per year. Moreover, the Saguenay River receives urban wastewaters and the bacterial populations in the surface waters are abundant and diversified. Among the organic matter from the paper mills, the abietic and dehydroabietic resin acids are very toxic for aquatic organisms. Yet, we found that, with endogenous populations of Bacillus psychrophilus in the decantation-basin, it was possible to oxidize the dehydroabietic acid (DHA), a non chlorinated resinic acid. It was found that after 72 hours, more than 92 % of this pollutant was oxidized. After a period of 96 hours, biodegradation was complete. The kinetics of this reaction were studied by measuring the fluctuations of the rates of ATP and by gas chromatography. We think that this bacterial species is thus probably an important microorganism controlling the toxicity of the wastewaters from the paper mills of the Saguenay.