CONTINUOUS COCULTURE DEGRADATION OF SELECTED POLYCHLORINATED BIPHENYL CONGENERS BY ACINETOBACTER SPP IN AN AEROBIC REACTOR SYSTEM

A coculture of two Acinetobacter spp. was applied to degrade polychlorinated biphenyls during a 42-day incubation study in a continuous aerobic fixed-bed reactor system, filled with polyurethane foam boards as support for bacterial biofilm development. The reactor was supplied with mineral medium containing 500 ppm sodium benzoate as a growth (primary) substrate, while the incoming airstream was saturated with biphenyl vapors to induce for PCB cometabolism in Acinetobacter sp. strain P6. The chlorobenzoates thus generated from 4,4′-di-chlorobiphenyl (4,4′-DCBP), 3,4-dichlorobiphenyl (3,4-D-CBP), and 3,3′,4,4′-tetrachlorobiphenyl were further metabolized by Acinetobacter sp. strain 4-CB1. The chlorobenzoate metabolites, as well as ring-físsion product (λmax = 442 nm) from the PCB congeners, accounted for the degradation of 63% (2.8 mM) of the 4,4′-DCBP, 100% (0.5 mM) of the 3,4-DCBP, and 32% (0.12 mM) of the 3,3′,4,4′-TCBP added. Respectively, 6.5% of 4,4′-DCBP and 11% of 3,4-DCBP were mineralized by the coculture. Upon application of a shock load of 4,4′-DCBP and 3,3′,4,4′-TCBP, the biofilm responded with a concurrent higher release of chlorobenzoates and chloride through cosubstrate utilization. Cosubstrate degradation kinetics of the PCBs and chlorobenzoates at concentrations below the affinity constant value (KM) showed that chlorobenzoate utilization rates were 6 times lower and chlorobiphenyl utilization rates 15 times lower than benzoate metabolization rates by both Acinetobacter spp. Continuous degradation by this stable coculture may thus provide a working model for biodegradation of other polychlorinated biphenyls. © 1990, American Chemical Society. All rights reserved.