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 toulene 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 CO2 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 constant for o-cresol-degrading biomass activity was estimated to be 0.15 h-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Flyvbjerg
J
J
Department of Environmental Engineering, Technical University of Denmark, Lyngby.
Jørgensen
C
C
Arvin
E
E
Jensen
B K
BK
Olsen
S K
SK
D001673:Biodegradation, Environmental; D041841:Bradyrhizobiaceae / Q000378:metabolism*; D003408:Cresols / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D007700:Kinetics; D008954:Models, Biological; D014050:Toluene / Q000378:metabolism*
D003408:Cresols; D003470:Culture Media; D014050:Toluene; C034047:2-cresol