Effect of Pleurotus ostreatus on Bioremediation of PAH Contaminated River Sediment

Abstract

The purpose of this study was to optimize bioremediation of Mahoning River sediment historically contaminated with polycyclic aromatic hydrocarbons (PAHs) using white rot fungi. Pleurotus ostreatus grown on grain (10% v/v) was added to contaminated sediment amended with sawdust (80% v/v), with and without fungal specific nutritional nitrogen (to enhance fungal growth), and with cyclodextrin (to increase PAH availability). Sediment mixtures were incubated in the dark at 25⁰C for 6 weeks. Sawdust made the sediment more porous, allowed better colonization by fungi, and did not greatly increase volume. Fungal biomass, determined using fluorescent microscopy, indicated initial fungal colonization but then fungal growth was inhibited, likely by toxic metals or high moisture content in the sediment. Growth of unidentified fungi was observed, especially in treatments amended with nitrogen. Total PAH concentrations (in the order of 100 ppm), analyzed using a gas chromatograph mass spectrometer (GCMS), and significantly decreased ̃ 50-60% in all treatments, including sediment only controls within the first two weeks. Thus, aerobic degradation by native bacteria and volatilization were likely responsible for most of the observed decreases in PAH concentrations. High heterogeneity of PAHs in this historically contaminated sediment led to high variance between replicates. There was a slight decrease in 5 ring PAHs associated with sediment inoculated with P. ostreatus and also a slight decrease in total PAH concentrations associated with sediment amended with sawdust and cyclodextrin (with or without P. ostreatus). Increased nitrogen did not enhance PAH degradation. Sediment inoculated with P. ostreatus after two weeks, rather than initially, showed better fungal growth and colonization, but PAH data was not yet available. These data indicate there is great potential for bioremediation of PAH contaminated sediment conditions by stimulating indigenous bacteria under aerobic conditions followed by the addition of wh