Purification, Characterization, and Immobilization of a Novel Protease-Resistant α-Galactosidase from Oudemansiella radicata and Its Application in Degradation of Raffinose Family Oligosaccharides from Soymilk

alpha-galactosidase (EC 3.2.1.22) are glycosidases that catalyze the hydrolysis of alpha-1,6-linked D-galactosyl residues of different substrates, which has been widely applied in the food industry. Oudemansiella radicata is a kind of precious edible medicinal mushroom, which is a healthy, green, and safe food-derived enzyme source. In this study, a novel acidic alpha-galactosidase was purified from the dry fruiting bodies of O. radicata by ion-exchange chromatography and gel filtration, and designated as ORG (O. radicata alpha-galactosidase). ORG was further immobilized to obtain iORG by the sodium alginate-chitosan co-immobilization method. Then, the characterization of free and immobilized enzymes and their potential application in the removal of the RFOs from soymilk were investigated. The results showed that ORG might be a 74 kDa heterodimer, and it exhibited maximum activity at 50 degrees C and pH 3.0, whereas iORG showed maximum activity at 50 degrees C and pH 5.5. In addition, iORG exhibited higher thermal stability, pH stability, storage stability, and a better degradation effect on raffinose family oligosaccharides (RFOs) in soymilk than ORG, and iORG completely hydrolyzed RFOs in soymilk at 50 degrees C within 3 h. Therefore, iORG might be a promising candidate in the food industry due to its excellent stability, high removal efficiency of RFOs from soymilk, and great reusability.

Automated summary

In this study, a novel acidic alpha-galactosidase was purified from Oudemansiella radicata and further immobilized to obtain iORG. The immobilized enzyme showed higher stability and better degradation effect on raffinose family oligosaccharides (RFOs) in soymilk, indicating its potential application in the food industry.