title: Enzymatic synthesis and identification of oligosaccharides obtained by transgalactosylation of lactose in the presence of fructose using β-galactosidase from Kluyveromyces lactis.
abstract: The enzymatic transgalactosylation of lactose in the presence of fructose using β-galactosidase from Kluyveromyces lactis (KlβGal) leading to the formation of oligosaccharides was investigated in detail. The reaction mixture was analyzed by high performance liquid chromatography with differential refraction detector (HPLC-RI) and two main transgalactosylation products were discovered. To elucidate their overall structures, the products were isolated and purified using preparative liquid chromatography and analyzed by LC/MS, one-dimensional (1D) and two-dimensional (2D) NMR studies. Allo-lactulose(β-d-galactopyranosyl-(1→1)-d-fructose) with two main isomers in D(2)O was identified to be the major transgalactosylation product while lactulose(β-d-galactopyranosyl-(1→4)-d-fructose) turned out to be the minor one, indicating that KlβGal was regioselective with respect to the primary C-1 hydroxyl group of fructose. The maximum yields of allo-lactulose and lactulose were 47.5 and 15.4g/l, respectively, at 66.5% lactose conversion (200g/l initial lactose concentration).
authors.affiliation: State Key Laboratory of Food Science & Technology and School of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi 214122, Jinangsu, China.
authors.forename: Qiuyun
authors.initials: Q
authors.lastname: Shen
authors.forename: Ruijin
authors.initials: R
authors.lastname: Yang
authors.forename: Xiao
authors.initials: X
authors.lastname: Hua
authors.forename: Fayin
authors.initials: F
authors.lastname: Ye
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Zhao
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
mesh_terms: D005632:Fructose / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D006031:Glycosylation; D007536:Isomerism; D007716:Kluyveromyces / Q000201:enzymology*; D007785:Lactose / Q000378:metabolism*; D007792:Lactulose / Q000737:chemistry* / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D005632:Fructose; D007792:Lactulose; D001616:beta-Galactosidase; D007785:Lactose