The filamentous fungus Aspergillus nidulans produces an α-L-rhamnosidase of potential oenological interest

The production of alpha-L-rhamnosidase by Aspergillus nidulans has been investigated. In the presence of rhamnose as sole carbon source, this fungus produces an alpha-L-rhamnosidase of molecular weight 90 kDa. Production of this enzyme is under carbon catabolite repression, apparently be a CreA-independent system. At acidic ambient pH there is an increase in the synthesis of the enzyme which is not related to PacC. Using rho-nitrophenyl-alpha-L-rhamnopyranoside as substrate, the enzyme activity in culture filtrates shows pH and temperature optima of 4.5-8 and 40-50 degrees C, respectively. At the concentrations found in must or wine, enzyme activity was only slightly affected by glucose and SO2 and partly inhibited by ethanol, indicating a potential for use in wine aroma release.