Journal article
Biodegradation of ortho-Cresol by a Mixed Culture of Nitrate-Reducing Bacteria Growing On Toluene
A mixed culture of nitrate-reducing bacteria degraded o-cresol in the presence of toluene as a primary growth substrate. No degradation of o-cresol was observed in the absence of toluene or when the culture grew on p-cresol and 2,4-dimethylphenol. In batch cultures, the degradation of o-cresol started after toluene was degraded to below 0.5 to 1.0 mg/liter but continued only for about 3 to 5 days after the depletion of toluene since the culture had a limited capacity for o-cresol degradation once toluene was depleted.
The total amount of o-cresol degraded was proportional to the amount of toluene metabolized, with an average yield of 0.47 mg of o-cresol degraded per mg of toluene metabolized. Experiments with (ring-U-14C)o-cresol indicated that about 73% of the carbon from degraded o-cresol was mineralized to CO-2 and about 23% was assimilated into biomass after the transient accumulation of unidentified water-soluble intermediates.
A mathematical model based on a simplified Monod equation is used to describe the kinetics of o-cresol degradation. In this model, the biomass activity toward o-cresol is assumed to decay according to first-order kinetics once toluene is depleted. On the basis of nonlinear regression of the data, the maximum specific rate of o-cresol degradation was estimated to be 0.4 mg of o-cresol per mg of biomass protein per h, and the first-order decay constants for o-cresol-degrading biomass activity was estimated to be 0.15 h-1.
We hypothesize that the mixed culture degrades o-cresol by a cometabolic mechanism in which the enzymes necessary for the degradation of o-cresol are induced by toluene and not by o-cresol.
Language: | English |
---|---|
Year: | 1993 |
Pages: | 2286-2292 |
ISSN: | 10985336 and 00992240 |
Types: | Journal article |
DOI: | 10.1128/aem.59.7.2286-2292.1993 |
ORCIDs: | Arvin, Erik |