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Appl. Environ. Microbiol., Nov 1997, 4216-4222, Vol 63, No. 11
RJ Steffan, K McClay, S Vainberg, CW Condee and D Zhang
Several propane-oxidizing bacteria were tested for their ability to degrade
gasoline oxygenates, including methyl tert-butyl ether (MTBE), ethyl
tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). Both a
laboratory strain and natural isolates were able to degrade each compound
after growth on propane. When propane-grown strain ENV425 was incubated
with 20 mg of uniformly labeled [14C]MTBE per liter, the strain converted
> 60% of the added MTBE to 14CO2 in < 30 h. The initial oxidation of
MTBE and ETBE resulted in the production of nearly stoichiometric amounts
of tert-butyl alcohol (TBA), while the initial oxidation of TAME resulted
in the production of tert-amyl alcohol. The methoxy methyl group of MTBE
was oxidized to formaldehyde and ultimately to CO2. TBA was further
oxidized to 2-methyl-2-hydroxy-1- propanol and then 2-hydroxy isobutyric
acid; however, neither of these degradation products was an effective
growth substrate for the propane oxidizers. Analysis of cell extracts of
ENV425 and experiments with enzyme inhibitors implicated a soluble P-450
enzyme in the oxidation of both MTBE and TBA. MTBE was oxidized to TBA by
camphor-grown Pseudomonas putida CAM, which produces the well-characterized
P-450cam, but not by Rhodococcus rhodochrous 116, which produces two P-450
enzymes. Rates of MTBE degradation by propane-oxidizing strains ranged from
3.9 to 9.2 nmol/min/mg of cell protein at 28 degrees C, whereas TBA was
oxidized at a rate of only 1.8 to 2.4 nmol/min/mg of cell protein at the
same temperature.
Copyright © 1997, American Society for Microbiology
Biodegradation of the gasoline oxygenates methyl tert-butyl ether, ethyl tert-butyl ether, and tert-amyl methyl ether by propane-oxidizing bacteria
Envirogen, Inc., Lawrenceville, New Jersey 08648, USA. steffan@envirogen.com
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