title: Reverse reaction of Aspergillus niger APC-9319 alpha-galactosidase in a supersaturated substrate solution: production of alpha-linked galactooligosaccharide (alpha-GOS).
abstract: The alpha-galactosidase that effectively catalyzes a reverse reaction of galactose, Aspergillus niger APC-9319 alpha-galactosidase, was screened from industrial enzyme preparations for food processing containing alpha-galactosidase activity. Reverse reaction of A. niger APC-9319 alpha-galactosidase was performed using a supersaturated solution (90% galactose [w/v]). A. niger APC-9319 alpha-galactosidase was not inhibited even in high substrate concentration, and effectively catalyzed the reverse reaction. The yield of the reaction product, alpha-linked galactooligosaccharide (alpha-GOS), increased greatly as the initial concentration of galactose increased to 90% (w/v), and was more than 50%. Furthermore, the half life of enzyme activity was about three times as long as that using 60% galactose (w/v). alpha-GOS (1.4 g) was prepared from galactose (3.0 g) by reverse reaction of A. niger APC-9319 alpha-galactosidase. The alpha-GOS contained 58% alpha-galactobiose (alpha-Gal2), 28% alpha-galactotriose, and 14% oligosaccharides larger than alpha-galactotriose. The main component of positional isomers in alpha-Gal2 was alpha-1,6Gal2.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Shinshu University, 8304 Minamiminowa, Nagano 399-4598, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Yamashita
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hashimoto
authors.forename: Koki
authors.initials: K
authors.lastname: Fujita
authors.forename: Masamichi
authors.initials: M
authors.lastname: Okada
authors.forename: Shigeharu
authors.initials: S
authors.lastname: Mori
authors.forename: Sumio
authors.initials: S
authors.lastname: Kitahata
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D004187:Disaccharides / Q000032:analysis / Q000378:metabolism; D005690:Galactose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods; D007700:Kinetics; D009844:Oligosaccharides / Q000032:analysis / Q000378:metabolism*; D015203:Reproducibility of Results; D013379:Substrate Specificity; D013696:Temperature; D014312:Trisaccharides / Q000032:analysis / Q000378:metabolism; D000519:alpha-Galactosidase / Q000378:metabolism*
chemical_list: D004187:Disaccharides; D009844:Oligosaccharides; D014312:Trisaccharides; D000519:alpha-Galactosidase; D005690:Galactose