Hydrolysis of oligosaccharides in soybean flour by soybean α-galactosidase

Raffinose oligosaccharicies (ROs) make up a substantial part (40%) of the soluble sugars found in soybean seeds and are responsible for flatulence after the ingestion of soybean and other legumes. Consequently, soy-based foods would find a broader approval if the ROs were removed from soybean products or hydrolysed by alpha-galactosidases. During soybean seed germination, of content the ROs decrease substantially, while the a-galactosidase activity increases. alpha-Galactosidase was partially purified from germinating seeds by partition in an aqueous two-phase system and ion-exchange chromatography. The enzyme preparation presented maximal activities against p-nitrophenyi-alpha-D-galactopyranoside (rho NPGal) at 60 degrees C and a pH of 5.0 and the K-Mapp values for rho NPGal, melibiose, and raffinose of the enzyme preparation were 0.33, 0.42, and 6.01 mM, respectively. The enzyme was highly inhibited by SDS, copper, and galactose. Hydrolysis of soybean flour ROs by enzyme preparation reduced the stachyose and raffinose contents by 72.3% and 89.2%, respectively, after incubation for 6 h at 40 degrees C. (c) 2004 Elsevier Ltd. All rights reserved.