Production and characterization of anAspergillus terteus ?-l-rhamnosidase of oenological interest

Abstract

Conditions for maximal batch culture production of extracellularα-L-rhamnosidase byAspergillus terreus have been investigated. Production of the enzyme appeared to be inducible by rhamnose and rutin, reaching a maximal level after an incubation period of 162 h when the fungus was grown at 37°C on either of these compounds as the carbon source and on ammonium phosphate as the nitrogen source. Nonionic surfactants did not enhanceα-L-rhamnosidase secretion. Under optimal conditions,A. terreus produced only oneα-L-rhamnosidase of approximate molecular weight 90 kDa (SDS-PAGE) and isoelectric point of 4.6. Onp-nitrophenyl-α-L-rhamnopyranoside as substrate, the enzyme showed pH and temperature optima of 6–8 and 45–50°C, respectively. Neither divalent cations nor ethylenediaminetetraacetate (EDTA) inhibited or stimulated enzyme activity. The enzyme was active at the concentrations of glucose found in must or of ethanol in wine.