Batch microcosm studies were carried out to screen for microorganisms from the
subsurface of Hanford DOE site that could cometabolically transform chloroform (CF)
under aerobic conditions. The potential need for CF bioremediation at the Hanford site
has resulted from the large release of carbon tetrachloride (CT) to the subsurface, of
which a fraction anaerobically transformed to CF. Potential cometabolic substrates were
screened for their ability to promote aerobic cometabolism of CF. The potential
cometabolic substrates tested were isoprene, propene, octane, ammonia, methane,
propane, and butane. Microcosms were constructed with 125 ml batch serum bottles
filled with 25 g of aquifer solids, 50 ml of synthetic groundwater, and 60 ml of headspace
air. Consumption of methane, butane, propane, and propene was slow, while the
consumption of ammonia was very slow. Microorganisms stimulated on propene and
octane showed no ability to transform CF. Limited CF was transformed in microcosms
stimulated on ammonia and methane. Over 90% transformation of CF was observed in
microcosms stimulated on either butane or propane during the initial incubation.
Successive addition studies with methane, propane, and butane microcosms were conducted, because these substrates showed the most potential for driving CF cometabolism. The studies indicated that the most effective CF transformation was achieved by butane-utilizers. CF transformation was correlated with the consumption of the primary substrate. Propane- and butane-utilizers grown in the absence of CF showed transformation yields 3 times greater than those grown in the presence of CF. In butane fed microcosms, CF transformation was linked with butane and oxygen consumption, indicating that an oxygenase enzyme of the butane-utilizers was likely responsible for CF transformation. The butane-utilizers showed no ability to transform CT, which also suggests the possibility of CF transformation by an oxygenase enzyme. In butane
microcosms, complete transformation of 55 pg of CF (1200 ��g/L of CF in aqueous
solution) was observed. The maximum transformation yield of 0.03 g CF transformed/g
substrates consumed was achieved by the butane-utilizers. A stoichiometric amount of
chloride was released to solution from CF during CF transformation, indicating that complete dehalogenation of CF was achieved by butane-utilizers. In our knowledge, these were the first observations, demonstrating butane as a cometabolic substrate for CF transformation. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34216 |
| Date | 04 September 1996 |
| Creators | Kim, Young |
| Contributors | Semprini, Lewis |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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