Isolation and identification of a yeast strain capable of degrading four and five ring aromatic hydrocarbons

Abstract

A yeast strain AEH was isolated from oil contaminated soil and identified by analysis of 18S and 26S ribosomal DNA sequences asPichia anomala. Strain AEH was capable of degrading naphthalene, phenanthrene and chrysene, singly, and benzo(a)pyrene in combination. The yeast degraded 5.36 mg naphthalene l⁻¹ within 2 days, and 5.04 mg phenanthrene l⁻¹ and 1.54 mg chrysene 1⁻¹ within 10 days. When a mixture of the four polycyclic aromatic hydrocarbons (PAHs) was treated at a concentration between 2.98 mg l⁻¹ and 6.89 mg l⁻¹, degradation rates were delayed for naphthalene and phenanthrene (3.79 mg l⁻¹ and, 4.20 mg l⁻¹ within 10 days, respectively), but enhanced for chrysene and benzo(a)pyrene (3.37 mg l⁻¹ and, 1.91 mg l⁻¹ within 10 days, respectively). In a binary system, all of the other 3 PAHs could be utilized as the carbon source for the cometabolic degradation of benzo(a)pyrene with naphthale ne as the best one.