Mycobacterium vaccae JOB5 and Graphium sp. were studied to
evaluate their ability to cometabolize methyl tert-butyl ether (MTBE) and its
metabolites after growth on two different alkanes, propane and iso-pentane.
Both cultures were capable of cometabolizing MTBE and the metabolites,
tert-butyl formate (TBF) and tert-butyl alcohol (TBA). MTBE, TBF, and TBA
did not support growth of either microbe. Higher degradation rates were
obtained in the bacterial system when the cultures were grown on iso-pentane.
Nonlinear least squares regression and direct linear plot methods
were used to estimate kinetic coefficients and provided comparable results. The enzymes from Mycobacterium vaccae JOB5 and Graphium sp. that promote the cometabolism of MTBE and its metabolites exhibited
similar kinetics and substrate inhibition. The presence of the substrate
decreased the degradation rate of MTBE and TBA suggesting competitive
inhibition and preference for the substrate. Blockage experiment with
acetylene suggested the presence of an alkane monooxygenase for the
metabolism of MTBE and TBA, and a hydrolytic enzyme for the degradation
of TBF. The presence of a hydrolase enzyme was supported by the fact
that TBF was degraded to TBA under either aerobic or anaerobic conditions
and was not inhibited by the presence of acetylene, propane, or isopentane.
Measured rates of abiotic hydrolysis of TBF were significantly
less than biodegradation rates.
Acetylene acted as a reversible inhibitor for both cultures when
tested in the presence of the growth media and as an inactivator when
tested in the presence of a phosphate solution for the bacterial system.
Growth-batch reactor experiments were conducted to compare the
degradation of iso-pentane and MTBE with the predicted degradation rates
based upon kinetic constants determined from single and dual-compound
experiments. Experimental data was modeled with Monod kinetics and
STELLA�� software. Reasonable predictions of reactor performance were
achieved when Monod maximum utilization rates were increased compared
to single and dual-compound experiments. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32417 |
| Date | 30 April 2002 |
| Creators | Mart��nez-Prado, Maria Adriana |
| Contributors | Williamson, Kenneth J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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