Adsorption of a fungal hydrophobin onto surfaces as mediated by the associated polysaccharide schizophyllan

Abstract

The filamentous fungus Schizophyllum commune secretes three major biopolymers into liquid growth media. These include a 24 kiloDalton hydrophobin, a 17 kiloDalton protein, and a high molecular mass polysaccharide, schizophyllan. The fungal culture supernatant forms sodium dodecyl sulfate resistant coatings on both hydrophobic and hydrophilic surfaces as demonstrated by water contact angle measurements and atomic force microscopy. Specific digestion of the schizophyllan from the supernatant has little effect on coating integrity on a hydrophobic surface. By contrast, enzymatic digestion of the hydrophobin eliminates the ability of the remaining supernatant components to assemble as a stable entity on a hydrophobic surface. Digestion of either the polysaccharide or the hydrophobin prevents stable association with a hydrophilic surface. Previous studies have demonstrated the role of hydrophobin in forming stable coatings on various surfaces; however, the synergistic interaction of schizophyllan with hydrophobin was not considered. Our data form the basis for a preliminary model in which hydrophobin is stabilized in the culture supernatant by a protective hydrophilic corona. Coalescence of hydrophobin onto solid mica or Parafilm® surfaces is favored over self-association in the presence of schizophyllan. © 1999 John Wiley & Sons, Inc. Biopoly 49: 621–633, 1999