Competition of Pleurotus sp. and Dichomitus squalens with soil microorganisms during lignocellulose decomposition

It has been suggested that white-rot fungi might be used in the bioremediation of soil contaminated with highly resistant pollutants. Under field conditions the fungus must not only be able to survive, but also be biologically active in the face of competition from the native soil microflora. In this study the competitive saprophytic capabilities of two species of white-rot fungi were evaluated in solid-state straw cultures in the presence of soil microorganisms. Pleurotus sp. strain Bhutan strongly inhibited growth of soil bacteria. Pleurotus cultures with or without soil microflora showed only small differences in the parameters: decomposition of organic matter, decomposition of lignin and pH, thus showing this fungus to be highly competitive with respect to the soil microorganisms. In contrast, in mixed cultures of Dichomitus squalens with soil microorganisms, bacterial growth was even higher than in sterile straw, while the decomposition of organic matter, especially of lignin, was much lower than in pure cultures of the fungus, thus indicating that the activity of the fungus, and perhaps even its ability to survive, were suppressed by the soil microorganisms.