Phenanthrene removal by Penicillium frequentans grown on a solid-state culture: effect of oxygen concentration

Phenanthrene removal by Penicillium frequentans was compared under aerobic and microaerophilic conditions in a solid culture amended with low quantities of an agricultural residue. An inoculum of P. frequentans grown on sugarcane bagasse pith was mixed with soil spiked with 200 mg l(-1) of phenanthrene, to obtain a final bagasse/soil ratio of 1:16. The C/N ratio was adjusted to 60 and the moisture content to 40%. The oxygen concentrations were adjusted to 20%, 10%, 5%, 2% and close to 0%, in the soil-gas phase for each treatment. There were statistically significant (p<0.05) differences in the metabolic activity at different oxygen concentrations, measured as CO2 production. Phenanthrene removal rates increased with oxygen concentration, reaching 52% removal after 17 days of incubation for the treatment with 20% O2. Nevertheless, oxygen-limited (microaerophilic) conditions did not preclude phenanthrene degradation.