TITLE

Multiple α-galactosidases from Aspergillus foetidus ZU-G1: purification, characterization and application in soybean milk hydrolysis

AUTHOR(S)
Liu, C.; He, G.
PUB. DATE
May 2012
SOURCE
European Food Research & Technology;May2012, Vol. 234 Issue 5, p743
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
α-Galactosidase had applied in food and feed industries for hydrolyzing raffinose series oligosaccharides (RO) that are the factors primarily responsible for flatulence upon ingestion of soybean-derived products. The objective of the current work was to purify the α-galactosidase of Aspergillus foetidus ZU-G1 and compared the biochemical and hydrolytic properties of three major α-galactosidase forms (α-gal I, α-gal II and α-gal III). The molecular mass of the purified enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was 106.3, 49.7 and 109.9 kDa, respectively. Its optimum reaction temperature was 60 °C and stable below 50 °C. The optimum pH of α-gal I and α-gal III was 5.0 and α-gal II was 4.0. Under 28 °C conditions for 24 h, α-gal I was stable at pH 4.0, α-gal II was stable at pH 6.0, and α-gal III was pH 5.0. α-Galactosidase was completely inhibited by Ag. CuSO·5HO and SDS were powerful inhibitors of α-gal I and α-gal III but had little effect to α-gal II. EDTA did not strongly affect α-gal I and α-gal III, while strongly affect α-gal II. CaCl·2HO, MgSO·7HO and MnSO·7HO were activation for α-gal I, α-gal II and α-gal III. No significant inhibition of enzymes activity was observed in the presence of raffinose, lactose as well as other sugars tested. Synthetic substrate p-nitrophenyl-α- d-galactopyranoside was not preferentially hydrolyzed than natural substrates, such as melibiose, stachyose and raffinose. Under 40 and 50 °C incubation for 1-5 h, the stachyose of soybean milk was degraded by α-gal I, α-gal II and α-gal III and strongly hydrolyzed by α-gal II, and the raffinose of soybean milk was completely hydrolyzed by α-gal II and weakly hydrolyzed by α-gal I and α-gal III. The distinct hydrolytic and biochemical properties of α-gal I, α-gal II and α-gal III further signify the α-galactosidase of A. foetidus ZU-G1 was propitious to soybean milk and related food industry.
ACCESSION #
74220480

 

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