Sepabeads EC-EP immobilized α-galactosidase: Immobilization, characterization and application in the degradation of raffinose-type oligosaccharides

Raffinose family oligosaccharides (RFOs) are mainly containing raffinose and stachyose. They are antinutrient compounds and the major factors responsible for the flatulence upon ingestion of soymilk. α-Galactosidases can hydrolyse RFOs to digestible oligosaccharides. α-Galactosidase was partially purified from watermelon and then immobilized on Sepabeads EC-EP with 56% of activity yield by determined best immobilization conditions. The optimum temperature and pH for both enzymes were found as 65 °C and pH 6.0, respectively. They showed an excellent stability between pH 3.0–7.0 and below 70 °C. The effect of several sugars and metal ions showed that both enzymes affected at different rates. Reusability of the immobilized enzyme with p NPG and raffinose as substrates indicated that the enzyme can be used for a long time with over 50% recovered activity. The enzymatic hydrolysis of the RFOs was realized and HPLC analysis demonstrated that 77.5% and 72.7% of the stachyose and raffinose presented in soymilk is hydrolyzed by the immobilized enzyme during 24 h incubation, respectively. This practical and alternative approach may be a potential to improve the nutritional value of soymilk by eliminating RFOs. Because of its high activity and stability properties the immobilized α-galactosidase may also find several applications in food and feed industries.