Production and characterization of extracellular α-galactosidase from Aspergillus oryzae DSM 1862

Abstract

The α-galactosidase is important industrial enzyme, used both in food and feed industry, that hydrolyses variety of non-digestible oligosaccharides with α-1,6-galactosydic bonds, thus allowing wider consumption of soybean-derived products [1,2]. The aim of this work was to produce this enzyme by submerged fermentation with Aspergillus oryzae DSM 1862 using several agricultural by-products (soybean meal, soybean flour, wheat bran, barley bran) as substrates. Soybean flour was proved to be the substrate of choice, being the most productive (3.34 IU/ml), and at the same time easiest for handling. In order to optimize cultural conditions for obtaining highly active preparations, different parameters were varied: substrate concentration (2-50 %), fermentation time (1-7 days), size of inoculum (0.5-5%). The highest activity was achieved after 6 days submerged fermentation using 2 % soybean flour and with 0.5 % of inoculum, since it showed no influence on produced activity. Furthermore, purification was performed by simple acetone precipitation and this was later proved by electrophoresis. The purified preparation was characterized, and it was concluded that optimal conditions for raffinose hydrolisis were 50 ᵒC and pH 4.8.