Effects of Poorly Metabolized Hydrocarbons on Substrate Oxidation by Cladosporium resinae

Twelve hydrocarbons which singly support no growth or little growth of Cladosporium resinae were examined for their effects on utilization of four substrates which do support growth of the fungus. Of the 48 combinations of an oxidizable substrate with a potential hydrocarbon substrate, 8 combinations supported increased oxygen consumption above the level obtained with the oxidizable substrate alone. There was no evidence of co-oxidation of the potential co-substrates toluene or p -xylene; their effects on increasing O₂-uptake appear to be due to permeability changes. With hexadecane alone, the ratio hexadecane oxidized to CO₂: hexadecane taken up by cells was 97:3. Addition of p -xylene or toluene decreased that ratio slightly to 96:4 and 89:11, respectively. These high ratios of hydrocarbon oxidized to hydrocarbon taken up may be advantageous during degradation of petroleum in the natural environment, since petroleum components could be degraded without formation of a large biomass.