Methanol suppression of trichloroethylene degradation by Methylosinus trichosporium (OB3b) and methane-oxidizing mixed cultures.
ABSTRACT The effect of methanol on trichloroethylene (TCE) degradation by mixed and pure methylotrophic cultures was examined in batch culture experiments. Methanol was found to relieve growth inhibition of Methylosinus trichosporium (OB3b) at high (14 mg/L) TCE concentrations. Degradation of TCE was determined by both radiolabeling and gas chromatography techniques. When cultures were grown on methanol over 10 to 14 d with 0.3 mg/L TCE, OB3b degraded 16.89 +/- 0.82% (mean +/- SD) of the TCE, and a mixed culture (DT type II) degraded 4.55 +/- 0.11%. Mixed culture (JS type I) degraded 4.34 +/- 0.06% of the TCE. When grown on methane with 0.3 mg/L TCE, 32.93 +/- 2.01% of the TCE was degraded by OB3b, whereas the JS culture degraded 24.3 +/- 1.38% of the TCE, and the DT culture degraded 34.3 +/- 2.97% of the TCE. The addition of methanol to cultures grown on methane reduced TCE degradation to 16.21 +/- 1.17% for OB3b and to 5.08 +/- 0.56% for JS. Although methanol reduces the toxicity of TCE to the cultures, biodegradation of TCE cannot be sustained in methanol-grown cultures. Since high TCE concentrations appear to inhibit methane uptake and growth, we suggest the primary toxicity of TCE is directed towards the methane monooxygenase.
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ABSTRACT: 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 (SIRANtrade mark 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 approximately 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 approximately 34%. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 674-685, 1997.Biotechnology and Bioengineering 08/1997; 55(4):674-85. · 4.16 Impact Factor
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ABSTRACT: Numerous technologies are readily available for on‐site above‐ground treatment of ground water contaminated with TCE. Proper delineation of the extent of the contamination in the vadose and the saturated zones and bedrock remains the main problem responsible for the disappointing record of the full‐scale remediation efforts so far. A comprehensive approach is advocated that combines the pump‐and‐treat technology and in situ remediation, with particular emphasis on biological processes, as the least cost alternative.Journal of Soil Contamination - J SOIL CONTAM. 01/1993; 2(3):205-228.
- Biotechnology and Bioengineering - BIOTECHNOL BIOENG. 01/1997; 55(4):674-685.