DEGRADATION OF POLYCYCLIC AROMATIC-HYDROCARBONS BY AN IMMOBILIZED MIXED BACTERIAL CULTURE

The mixed bacterial culture MK1 was capable of degrading a wide spectrum of aromatic compounds both as free and as immobilized cells. By offering anthracene oil or a defined mixture of phenol, naphthalene, phenanthrene, anthracene and pyrene (in concentrations of 0.1-0.2 mM, respectively) as sources of carbon and energy, a specific degradation pattern correlating with the condensation degree was observed. Regarding the defined mixture of aromatic hydrocarbons, complete metabolism was reached for phenol (0.1 mM) after 1 day, for naphthalene (0.1 mM) after 2 days and for phenanthrene (0.1 mM) after 15 days of cultivation. The conversion of anthracene (0.1 mM) and py rene (0.1 mM) resulted in minimal residual concentrations, analogous to fluoranthene and pyrene of the anthracene oil (0.1%). Maximal total degradation for the tricyclic compounds dibenzofurane, fluorene, dibenzothiophene, phenanthrene and anthracene of the anthracene oil (0.1%) occurred after 5 days. In general, a significant metabolisation of the tetracyclic aromatic hydrocarbons fluoranthene and pyrene was observed after the degradation of phenol, naphthalene and most of the tricyclic compounds. Doubling the start concentrations of the polycyclic aromatic hydrocarbons effected higher degradation rates. Cell growth occurred simultaneously with the conversion of phenol, naphthalene and the tricyclic compounds. The immobilized cells showed stable growth and, compared to freely suspended cells, the same degradation sequence as well as an equivalent degradation potential - even in a model soil system.