Enrichment and Characterization of Resin Acid Degrading Bacteria from Bleached Kraft Effluents, 1994 Environmental Conference Proceedings

P.A. Bicho, V. Martin, J. N. Saddler

Pulp mill effluent treatment systems occasionally experience toxicity breakthroughs. In these situations, treatment parameters such as COD, BOD and TSS are within regulatory guidelines yet effluents are still acutely toxic. Resin acids are wood extractives which contribute significantly to pulp mill effluent toxicity and have been implicated in these toxicity breakthroughs. The biological mechanisms of resin acid degradation are poorly understood. One approach to determining the factors which affect resin acid removal focuses on the isolation and characterization of the bacteria responsible for resin acid biodegradation in effluent treatment systems. An enrichment and isolation protocol was established using effluent and sludge from the treatment systems of two bleached kraft mills and one CTMP mill. Over twenty isolated that degrade dehydroabietic acid (DHA), a common and persistent resin acid, were obtained. Some of the isolates consumed 200 mg/L of DHA within five days. Many degraded pimarate as well as other abietene type resin acids. The predominant isolates were Gram negative, aerobic rods. Biochemical typing showed that the isolates had some physiological similarities but were taxonomically distinct. Physiological studies investigating the growth of these isolates in defined media with DHA and other resin acids provided specific rates of degradation and biomass yields. Similar experiments with filter-sterilized effluents determined the effects of other components of pulp mill effluents on the efficiency of resin acid biodegradation.