Ligninolytic activity of white rot fungi and their efficiency in bioremediation

Abstract

Wooden railway sleepers impregnated with creosote or coal tar are protected from wood-degrading microorganisms. Coal tars and creosote are complex and variable mixtures of polycyclic aromatic hydrocarbons (PAH), phenols and heterocyclic compounds. Bioremediation using various microorganisms is one of the ways to remove PAHs from the environment. There are three known different pathways of microbial degradation; the basis of these mechanisms is the oxidation of the aromatic ring. PAH-degrading microorganisms are divided in three groups: bacteria, non-ligninolytic fungi and ligninolytic fungi. Ligninolytic fungi like Pleurotus ostreatus, Irpex lacteus, Pleurotus eryngii or others, produce extracellular enzymes with very low substance specifity. This is supposed to be advantageous for the degradation of PAHs. Ligninolytic system of white rot basidiomycetes consists of a pool of enzymes, namely laccases, lignin peroxidase, versatile peroxidase, cellobiose dehydrogenase, H2O2-producing enzymes and reactive oxygen species produced by such enzymes. The aim of this research consists in the determination of fungi ligninolytic activity and the determination of the efficiency of different fungal species for the degradation of PAH. Five different species of fungi (Pleurotus ostreatus SMR 684, Pleurotus eryngii VMU001, Bjerkandera adusta VMU004, Irpex lacteus VMU003 and Schizophyllum commune VMU002) demonstrate degradation activity of different concentrations of treated railway sleepers. Composition of coal tar in railway wooden sleepers was determined using GC-MS and GC-FID.