Biochemistry and ecology of resin acid biodegradation in pulp and paper mill effluent treatment systems

Abstract

A better understanding of the mechanisms and ecology of resin acid biodegradation will contribute to improved performance of existing treatment systems and development of new treatment systems for pulp and paper mill effluents. Using molecular genetic methods, we have partially elucidated the biochemical pathway for degradation of abietane resin acids by Pseudomonas abietaniphila BKME-9. We identified genes encoding putative membrane-associated proteins that are required for abietane metabolism. These proteins may function in cellular uptake of, or response to, resin acids. Genetic and physiological evidence suggests that a monooxygenase is involved in the biochemical pathway. A quantitative PCR assay was developed for ditA1, a gene from BKME-9 encoding resin acid degradation. In an aerated lagoon treating pulp mill effluent, a population carrying ditA1 was found, which was a small fractton (10⁻⁷ of the total microbial community. This population was evenly distributed throughout the system and was a stable member of the community over time. Quantitative PCR assays were used to monitor Pseudomonas abietaniphila BKME-9 and Zoogloea resiniphila DhA-35 when they were separately used to inoculate a complex microbial communities in laboratory sequencing batch reactors. Both inocula were stably maintained in the community for 24 days. These inocula stimulated resin acid removal by the community when it was stressed by high pH or by high resin acid loading.