Isolation and the remediation potential of a Laccase-producing Soil Fungus F-5

Policyclic aromatic hydrocarbons (PAHs) are a class of organic compounds containing two or more fused aromatic rings, and composed of only carbon and hydrogen atoms. They are persistent organic pollutants (POPs) that exist extensively in environment. The United States Environmental Protection Agency (USEPA) has classified 16 of the PAHs as priority pollutants based on toxicity, potential for human exposure, frequency of occurrence at hazardous waste sites, and the extent of information available. The environmental risk cannot be ignored due to the possible carcinogenic, teratogenic and mutagenic effects of some high-molecular-weight PAHs. PAHs are widespread in the soil in some economically well-developed areas of China, such as Bohai Bay Rim, the Yangtze River and Pearl River Delta regions. In some cases, the concentration of PAHs has already reached a very high level in the soil of these regions. Laccases (EC1.10.3.2) are copper-containing oxidase enzymes that are found in many plants, fungi, and microorganisms. Because laccase have the ability to oxidize many kinds of organic pollutants, application potential of laccase in remediating organic contaminated soil has drawn extensive attention. Fungus is an essential part of the soil ecosystem, which plays an important role in the detoxification and cleaning up of organic contaminated soil. Many studies have shown that PAHs can be degraded efficiently by white-rot fungi, which usually grows on dead trees. However, white-rot fungi is not suitable to grow in soil and have limited application in soil remediation. Fungi with laccase-producing activity can transform and degrade PAHs. Thus, isolating PAHs-degrading fungi can be changed into isolating fungi with laccase-producing activity, which can simplify isolation procedure and save isolation time and work capacity. Isolating soil Fungi with high laccase-producing activity is promising to provide biological source for remediating PAHs-contaminated soil. Based on the phenomenon that media containing guaiacol can turn red, potent PAHs-transforming fungi strains can be isolated from soil. In this study, one fungal strain, F-5, was isolated from an agricultural soil based on the color development of guaiacol in medium. Analysis of partial 18S rRNA gene sequences showed that strain F-5 is affiliate within the Family Magnaporthaceae. Sucrose and peptone are the optimal carbon and nitrogen sources for laccase production respectively, according to one-factor experimen