A simple method for purifying glycosidases: alpha-L-rhamnopyranosidase from Aspergillus niger to increase the aroma of Moscato wine

alpha-L-rhamnopyranosidase (Rha. EC 3.2.1.40) is an enzyme of considerable importance in food technology for increasing the aroma of wines. musts, fru it juices and other alcoholic beverages. The aim of this research is to stu dy the purification of Rha contained in a commercial preparation already us ed in the winemaking industry. With the procedure adopted, Rha recovery Val ues were excellent (ca 85%), comparable with those we found in a previous p aper on the purification of other glycosidases such beta-D-glucopyranosidas e (beta G) and alpha-L-arabinofuranosidase (Ara) [1]. The Rha purification value (4.3) and drastic reduction in brown compounds (Delta Abs 95%) repres ent other strengths of the proposed method that has proved inexpensive and simple to apply. In addition, purified Rha has shown itself to be more stab le than other glycosidases. This had optimum effect at pH 4, while optimum temperature was 70 degrees C, greater than that found for other glycosidase s. The purified enzyme was characterized in terms of the kinetic parameters K-m (1.40 mM) and V-max (1.30 U mg(-1) of protein) and subsequently used t o increase aroma a model wine solution containing aromatic precursors extra cted from the skins of Moscato grapes, with an increase in the content of t otal terpenols of ca 2.3 times. (C) 2000 Elsevier Science Inc. All rights r eserved.