Phenanthrene Degradation Potential of Lignolytic Manglicolous Filamentous Fungus Trichoderma Sp. CNSC-2

Abstract

Manglicolous filamentous fungi are ecologically important fungal communities involved in the degradation of organic compounds. Extracellular lignolytic enzymes released by mangrove fungi have better physiochemical and catabolic properties than their terrestrial counterparts. Fungal enzymes can degrade various xenobiotic compounds and carry bioremediation potential. In the present study, the manglicolous fungus Trichoderma sp. CNSC-2, isolated from the Indian Sundarban mangrove ecosystem, is explored for its ability to degrade polycyclic aromatic hydrocarbon (PAH) and determine the role of lignolytic enzyme in PAH degradation. Phenanthrene is a toxic, highly persistent, bioaccumulative three-ringed PAH with various adverse effects on surrounding. Trichoderma sp. CNSC-2 effectively reduces 50 mg l-1 phenanthrene concentration up to 64.05±0.75% within 10 days of incubation without further optimization. The degradation rate was further optimized under various pH, nutrient source, and Cu2+ concentrations. The involvement of the extracellular laccase enzyme was determined by ABTS assay. Laccase enzyme activity was found to be higher in the presence of phenanthrene on day 6 of incubation which coincided with the phenanthrene removal rate. The addition of enzyme inhibitor simultaneously reduced the enzyme activity and degradation rate indicating major role of laccase in phenanthrene degradation. The Lac1 gene encoding for the laccase enzyme was identified. Further, GC-MS analysis revealed phenanthrene degradation metabolites, phthalic acid, isobutyl 2-pentyl ester derivative; 1, 2 benzene dicarboxylic acid, butyl 2-methyl propyl ester derivative; TMS derivative of benzoic acid and 3,5 dihydroxy benzoic acid determining two possible metabolic pathways catalyzed by fungal laccase. The effect of enzyme inducers on laccase enzyme activity was observed by the addition of Cu2+ ion. Laccase activity was significantly higher in Phe+Cu2+ and Cu2+ induced culture over control (P