Production and characterization of an extracellular Mn2+ activated ß-D-fructofuranosidase from Aspergillus labruscus ITAL 28.255 with transfructosylating activity

Abstract

Fungal ß-D-fructofuranosidases present biotechnological potential for use in food, beverage, and pharmaceutical industries. In light of this, the best culture conditions for the production of ß-D-fructofuranosidase by Aspergillus labruscus ITAL 28.255 were obtained with an M-5 medium maintained at 30°C and 100 rpm for 120 h. The use of a mixture of rye flour and sucrose (1.5:0.5, m/m) and 2% yeast extract as the carbon and nitrogen sources, respectively, proportioned the best production of the enzyme. The extracellular ß-D-fructofuranosidase was purified 17-fold, with 9% recovery, and was characterized as a glycoprotein with 67 kDa (SDS-PAGE) and 40.7% carbohydrate content. The best temperature and pH for enzyme activity were 55°C and 5.5, respectively. The enzyme activity was maintained around 75% at 40 and 50°C for 1 h, with a half-life of 5 min at 70°C. The hydrolytic activity was increased in the presence of Mn2+. The Vmax and KM were 4.74 mM and 140.3 U/mg using sucrose; while, in the presence of Mn2+, the KM was 2.17 mM and the Vmax was 292.9 U/mg. The enzyme performed the transfructosylation reaction, enabling the production of FOS, mainly 1-kestose. This is the first report on the potential of A. labruscus to produce β-fructofuranosidase with transfructosylation activity.