BACTERIA OBTAINED FROM A SEQUENCING BATCH REACTOR THAT ARE CAPABLE OF GROWTH ON DEHYDROABIETIC ACID

Eleven isolates capable of growth on the resin acid dehydroabietic acid (DhA) were obtained from a sequencing batch reactor designed to treat a high-strength process stream from a paper mill, The isolates belonged to two groups, represented by strains DhA-33 and DhA-35, which were characterized, In the bioreactor, bacteria like DhA-35 were more abundant than those like DhA-33, The population in the bioreactor of organisms capable of growth;on DhA was estimated to be 1.1 x 10(6) propagules per mi, based on a most-probable-number determination, Analysis of small-subunit rRNA partial sequences indicated that DhA-33 was most closely related to Sphingomonas yanoikuyae (S-ab = 0.875) and that DhA-35 was most closely related to Zoogloea ramigera (S-ab = 0.849). Both isolates additionally grew on other abietanes, i.e., abietic and palustric acids, but not on the pimaranes, pimaric and isopimaric acids, For DhA-33 and DhA-35 with DhA as the sole organic substrate, doubling times were 2.7 and 2.2 h, respectively, and growth yields were 0.30 and 0.25 g of protein per g of DhA, respectively, Glucose as a cosubstrate stimulated growth of DhA-33 on DhA and stimulated DhA degradation by the culture, Pyruvate as a cosubstrate did not stimulate growth of DhA-35 on DhA and reduced the specific rate of DhA degradation of the culture. DhA induced DhA and abietic acid degradation activities in both strains, and these activities were heat labile, Cell suspensions of both strains consumed DhA at a rate of 6 mu mol mg of protein(-1) h(-1). On the basis of this consumption rate, the estimated population of organisms capable of growth on DhA is at the lower limit required to account for DhA removal in the bioreactor, Both isolates have very similar resin acid degradation activities, which, because of their specificities for abietanes, can only partly account for resin acid removal in the bioreactor from which the strains were isolated.