Processing of soybean products by semipurified plant and microbial α-Galactosidases

Abstract

Galactooligosaccharides (GO) are responsible for intestinal disturbances following ingestion of legume-derived products. Enzymatic reduction of GO level in these products is highly desirable to improve their acceptance. For this purpose, plant and microbial semipurified α-galactosidases were used for GO hydrolysis in soybean flour and soy molasses. α-Galactosidases from soybean germinating seeds, Aspergillus terreus, and Penicillium griseoroseum presented maximal activities at pH 4.0−5.0 and 45−65 °C. The KM,app values determined for raffinose by the soybean, A. terreus, and P. griseoroseum α-galactosidases were 3.44, 19.39, and 20.67 mM, respectively. The enzymes were completely inhibited by Ag+ and Hg2+, whereas only soybean enzyme was inhibited by galactose. A. terreus α-galactosidase was more thermostable than the enzymes from the other two sources. This enzyme maintained about 100% of its original activity after 3 h at 60 °C. The microbial α-galactosidases were more efficient for reducing GO in soybean flour and soy molasses than soybean enzyme.