Role of Aspergillus oryzae rolA in 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. High levels of RolA and its localization on the cell surface in the presence of PBSA were confirmed by immunostaining. Under these conditions, A. oryzae simultaneously produced cutinase CutL1, which hydrolyzes PBSA. 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 CutLl on the PBSA surface and consequent stimulation of PBSA hydrolysis.