The purpose of this study is to investigate degradation and elimination, by Mycobacterium sp.H2-5, of high-molecular-weight polycyclic aromatic hydrocarbons (HPAH) in heavy oil, which washed ashore on Mikuni-cho in Fukui Prefecture, after leaking from a wrecked Russian oil tanker, the Nakhodka.
1.Degradation of HPAH in the heavy oil.
H2-5 was cultivated on the heavy oil, which was coated on glass beads, in mineral medium at 30℃ for 20 days. Benz[a]anthracene, pyrene, benzo[a]pyrene, and benzo[ghi]perylene in the heavy oil that had washed ashore disappeared by 99%, 92%, 60%, and 33%, respectively. These HPAH in commercial heavy oil (class C) disappeared by 92%, 99%, 60%, and 10%, respectively.
2.Metabolites in pyrene degradation by H2-5.
Meta bolites on pyrene degradation by H2-5 were extracted by ethyl acetate and analyzed by thin layer chromatography, resulting in 8 spots. Among them, the substance having an RィイD2fィエD2 value of around 0.19 was considered to be dihydroxynaphthoic acid from HPLC, Ms, and H-NMR analyses. One of the spots had a similar RィイD2fィエD2 value (around 0.35) to catechol ; however, the H-NMR signals were different from each other. The latter substance was separated into 3 peaks by HPLC, and two of them had the same UV spectra.
3.Mutagenicity of the culture of H2-5 on the heavy oil that washed ashore.
H2-5 was cultivated for 60 days under the same condition in 1. Mutagenicity levels of the benzene extracts were the same or tended to decrease compared with that of the control. Since mutagenicity was not found in the aqueous layer, increasing of mutagenicity did not occur through the treatment with H2-5.