The fungal hydrophobin RolA promotes PBSA degradation

When an industrial fungus Aspergillus oryzae was cultivated in liquid medium containing the biodegradable polyester polybutylene succinate-coadipate (PBSA), the rolA gene encoding hydrophobin RolA was highly transcribed. Preincubation of PBSA with RolA stimulated PBSA degradation by CutL1, suggesting that RolA bound to a PBSA surface was required for the stimulation. Immunostaining revealed that PBSA films coated with RolA specifically adsorbed CutL1. QCM analyses further demonstrated that RolA attached to a hydrophobic sensor chip specifically adsorbed CutL1. These results suggest that RolA adsorbed to the hydrophobic surface of PBSA recruits CutL1, resulting in condensation of CutL1 on the PBSA surface and consequent stimulation of PBSA hydrolysis. A fluorescence recovery after photobleaching (FRAP) experiment on PBSA films coated with FITC-labeled RolA suggested that RolA moves laterally on the film.