Degradation of chlorinated dioxins and polycyclic aromatic hydrocarbons (PAHs) and remediation of PAH-contaminated soil by the entomopathogenic fungus, Cordyceps militaris

• Cordyceps militaris was able to degrade polyCDDs and PAHs.
• Hydroxylation of aromatic rings is suggested as the initial metabolic step.
• Chitin promoted bioremediation in un-sterilized PAH-contaminated soil.
• Cordyceps militaris will be useful for bioremediation of contaminated soil.

Cordyceps militaris was able to metabolize dichloro-, trichlorodibenzo-p-dioxin, trichlorodibenzofuran, and 3–5 ring polycyclic aromatic hydrocarbons into their corresponding hydroxides. To investigate whether C. militaris has potential for use in soil remediation, fungal mycelia and BSM containing chitin or glucose were added to phenanthrene-contaminated soil. The phenanthrene was degraded more rapidly with chitin-BSM (50.1% in un-sterile soil in 4 weeks) than with glucose-BSM (7.4%). These results suggested that in un-sterilized soil, the indigenous soil microorganisms were not activated by chitin, and so the mycelial growth and/or phenanthrene-degrading ability of C. militaris were not inhibited. Small amounts of mycelia and chitin-BSM were added to the pyrene-contaminated soil, and the mixture was incubated for 2 months. Under these conditions, C. militaris degraded pyrene in both sterile (14.2%) and non-sterile soil (12.0%). A metabolite of pyrene, pyrenol, was detected in the sterile contaminated soil inoculated with the fungus. These results showed the possibility of efficient bioremediation for the aromatic pollutants (such as PAHs) contaminated soil using entomopathogenic fungi with chitin.