Section 11
Chapter 10,596

Enzymatic synthesis of galactosyl-xylose by Aspergillus oryzae beta-galactosidase

Giancomini, C.; Irazoqui, G.; Gonzalez, P.; Batista Viera, F.; Brena, B.M.

Journal of Molecular Catalysis B Enzymatic (19-20): 159-165, 2 December


ISSN/ISBN: 1381-1177
Accession: 010595394

In aqueous medium, the reaction catalyzed by Aspergillus oryzae beta-galactosidase with O-nitrophenyl-beta-D-galactopyranoside (ONPG) in the presence of an acceptor leads to the synthesis of transglycosylation compounds in addition to the hydrolysis products (ONP and galactose). Our goal was to develop a simple system for the synthesis of galactosyl-xylose, a disaccharide of possible application to diagnostics. To maximize synthesis yields, we have studied the effect of several conditions: increase of acceptor concentration (0.05-2.7 M xylose), organic co-solvents (dimethylformamide, acetone) and reaction time. In the absence of co-solvents ONPG was completely consumed in 2 h; with 0.5 M xylose the maximum yield of galactosylxylose (16%) was attained at 60 min, while with 2.7 M xylose the yield reached 21%. Both co-solvents tested decreased the kinetics of ONPG conversion into products and 50% (v/v) dimethylformamide was deleterious to the synthesis. However, in 50% (v/v) acetone the synthesis yield was 12% and interestingly, the proportion of transglycosylation with respect to the reacted substrate was higher than in buffer. The synthesis of galactosyl-ethyleneglycol was also studied; it was achieved with extremely high yield and no detectable hydrolysis products. This proves that other acceptor alcohols can be preferred over water in some conditions.

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