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

Eleven isolates capable of growth on the resin acid dehydroabietic aci d (DhA) were obtained from a sequencing batch reactor designed to trea t a high-strength process stream from a paper mill, The isolates belon ged to two groups, represented by strains DhA-33 and DhA-35, which wer e characterized, In the bioreactor, bacteria like DhA-35 were more abu ndant than those like DhA-33, The population in the bioreactor of orga nisms capable of growth;on DhA was estimated to be 1.1 x 10(6) propagu les per mi, based on a most-probable-number determination, Analysis of small-subunit rRNA partial sequences indicated that DhA-33 was most c losely 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 palus tric acids, but not on the pimaranes, pimaric and isopimaric acids, Fo r DhA-33 and DhA-35 with DhA as the sole organic substrate, doubling t imes 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 cosubstrat e stimulated growth of DhA-33 on DhA and stimulated DhA degradation by the culture, Pyruvate as a cosubstrate did not stimulate growth of Dh A-35 on DhA and reduced the specific rate of DhA degradation of the cu lture. DhA induced DhA and abietic acid degradation activities in both strains, and these activities were heat labile, Cell suspensions of b oth 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 o rganisms capable of growth on DhA is at the lower limit required to ac count for DhA removal in the bioreactor, Both isolates have very simil ar resin acid degradation activities, which, because of their specific ities for abietanes, can only partly account for resin acid removal in the bioreactor from which the strains were isolated.