| Summary: | The aerobic transformation of TCE and cis-DCE by a tetrabutoxysilane-grown
microorganism (Vancheeswaran et al., 1999) led to the investigation of novel
substrates, including benzyl alcohol, for promoting cometabolism. The culture grew
on carboxylic compounds and alcohols, but did not grow on formate, methanol,
methane, propane, butane, ethylene, benzene, toluene, or p-xylene. Cis-DCE
transformation was observed when the culture grew on butyrate, glucose, 1-propanol,
1-butanol, ethanol, benzyl alcohol, and phenol, and effectively transformed TCE, cis-DCE, and vinyl chloride when grown on phenol or benzyl alcohol.
Several cycles of growth on benzyl alcohol led to increases in TCE
transformation rates and transformation capacities. Products of benzyl alcohol
degradation shifted from benzaldehyde to 2-hydroxy benzyl alcohol (2HBA) during
the several cycles of growth. In resting cells studies, 2HBA production rates were
highly correlated with TCE transformation rates. TCE transformation and 2HBA
production rates doubled when the culture was grown on phenol and rates of TCE
transformation were correlated with 2HBA production rates. Benzyl alcohol- and
phenol-grown cells oxidized toluene to o-cresol, which indicated the similarity
between benzyl alcohol ortho-monooxygenase, phenol hydroxylase, and toluene
ortho-monooxygenase. 2-Butyne and 1-hexyne (but not acetylene) inhibited benzyl
alcohol- and phenol-grown cells similarly, indicating the same ortho-monooxygenase
was responsible for TCE cometabolism.
Resting cell kinetic studies were performed with cells grown on phenol or
benzyl alcohol. Benzyl alcohol degradation followed a Monod kinetics while phenol
degradation followed a Haldane kinetics. The maximum transformation rates (k[subscript max]) of
TCE, cis-DCE, and VC achieved by phenol-grown cells were about a factor of two
higher than achieved with benzyl alcohol-grown cells, while the half-saturation
constants (K[subscript s]) were in a similar range. Transformation capacities (Tc) for TCE, cis-DCE, and VC were about a factor of two to four higher with phenol-grown cells. The
modeling of TCE, cis-DCE, and VC transformation using independently measured
k[subscript max] and K[subscript s] values matched well with observed data from batch tests. Benzyl alcohol
was shown to be an effective novel substrate for the aerobic cometabolism of TCE,
cis-DCE, and vinyl chloride. Being a non-regulated compound, it might have
applications for in-situ bioremediation. === Graduation date: 2004
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