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Trichloroethylene mineralization in a fixed‐film bioreactor using a pure culture expressing constitutively toluene ortho ‐monooxygenase
Author(s) -
Sun Adam K.,
Wood Thomas K.
Publication year - 1997
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19970820)55:4<674::aid-bit9>3.0.co;2-e
Subject(s) - trichloroethylene , bioreactor , mineralization (soil science) , chemistry , biofilter , chloride , biodegradation , nuclear chemistry , toluene , burkholderia , chromatography , environmental chemistry , organic chemistry , environmental engineering , bacteria , biology , nitrogen , engineering , genetics
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 PR1 23 (TOM 23C ), 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 <1 day at 2.42 mg/L), although the biofilter could be operated for longer periods at lower TCE concentrations. Using an oxygen probe and phenol as the substrate, the activity of TOM in the effluent cells of the bioreactor was monitored; the loss of TOM activity of the effluent cells corroborated the decrease in the TCE degradation and mineralization rates in the bioreactor. Repeated starving of the cells was found to restore TOM activity in the bioreactor with activated carbon and extended TCE mineralization by ∼34%. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55 : 674–685, 1997.