Trichloroethylene mineralization in a fixed-film bioreactor using a pure culture expressing constitutively toluene ortho -monooxygenase

An aerobic, single‐pass, fixed‐film bioreactor was designed for the continuous degradation and mineralization of gas‐phase trichloroethylene (TCE). A pure culture of Burkholderia cepacia PR123(TOM23C), a Tn5transposon mutant of B. cepacia G4 that constitutively expresses the TCE‐degrading enzyme, toluene ortho‐monooxygenase (TOM), was immobilized on sintered glass (SIRAN™ carriers) and activated carbon. The inert open‐pore structures of the sintered glass and the strongly, TCE‐absorbing activated carbon provide a large surface area for biofilm development (2–8 mg total cellular protein/mL carrier with glucose minimal medium that lacks chloride ions). At gas‐phase TCE concentrations ranging from 0.04 to 2.42 mg/L of air and 0.1 L/min of air flow, initial maximum TCE degradation rates of 0.007–0.715 nmol/(min mg protein) (equivalent to 8.6–392.3 mg TCE/L of reactor/day) were obtained. Using chloride ion generation as the indicator of TCE mineralization, the bioreactor with activated carbon mineralized an average of 6.9–10.3 mg TCE/L of reactor/day at 0.242 mg/L TCE concentration with 0.1 L/min of air flow for 38–40 days. Although these rates of TCE degradation and mineralization are two‐ to 200‐fold higher than reported values, TOM was inactivated in the sintered‐glass bioreactor at a rate that increased with increasing TCE concentration (e.g., in ∼2 days at 0.242 mg/L and