Hydrolysis of galacto-oligosaccharides in soy molasses by α-galactosidases, invertase from Aspergillus terreus

Abstract

Two α-galactosidase (P1 and P2) and one invertase present in the culture of Aspergillus terreus grown on wheat straw for 168 h at 28°C were partially purified by gel filtration and hydrophobic interaction chromatographies. Optimum pH and temperatures for P1, P2 and invertase preparations were 4.5-5.0, 5.5 and 4.0 and 60, 55 and 65°C, respectively. The KM app for ρ-nitrophenyl-α-D-galactopyranoside were 1.32 mM and 0.72 mM for P1 and P2, respectively, while the KM app value for invertase, using sacarose as a substrate was 15.66 mM. Enzyme preparations P1 and P2 maintained their activities after pre-incubation for 3 h at 50°C and invertase maintained about 90% after 6 h at 55 °C. P1 and P2 presented different inhibition sensitivities by Ag+, D-galactose, and SDS. All enzyme preparations hydrolyzed galacto-ologosaccharides present in soymolasses.