ELECTRON AND FLUORESCENCE MICROSCOPY OF EXTRACELLULAR GLUCAN AND ARYL-ALCOHOL OXIDASE DURING WHEAT-STRAW DEGRADATION BY PLEUROTUS-ERYNGII

The ligninolytic fungus Pleurotus eryngii grown in liquid medium secre ted extracellular polysaccharide (87% glucose) and the H2O2-producing enzyme aryl-alcohol oxidase (AAO). The production of both was stimulat ed by wheat-straw. Polyclonal antibodies against purified AAO were obt ained, and a complex of glucanase and colloidal gold was prepared. Wit h these tools, the localization of AAO and extracellular glucan in myc elium from liquid medium and straw degraded under solid-state fermenta tion conditions was investigated by transmission electron microscopy ( TEM) and fluorescence microscopy. These studies revealed that P. eryng ii produces a hyphal sheath consisting of a thin glucan layer, This sh eath appeared to be involved in both mycelial adhesion to the straw ce ll wall during degradation and AAO immobilization on hyphal surfaces,, vith the latter evidenced by double labeling. AAO distribution during differential degradation of straw tissues was observed by immunofluore scence microscopy. Finally, TEM immunogold studies confirmed that AAO penetrates the plant cell wall during P. eryngii degradation of wheat straw.