Enzymatic Synthesis and Identification of Two Trisaccharides Produced from Lactulose by Transgalactosylation

• Published in: Journal of agricultural and food chemistry Vol. 56; no. 2; pp. 557 - 563
• Main Authors: Martínez-Villaluenga, Cristina, Cardelle-Cobas, Alejandra, Olano, Agustín, Corzo, Nieves, Villamiel, Mar, Jimeno, Maria Luisa
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 23.01.2008
• Subjects: beta-galactosidase; beta-Galactosidase - metabolism; Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; Carbohydrate Conformation; Carbohydrate Sequence; chemical reactions; Chromatography, High Pressure Liquid; enzymatic hydrolysis; Food Chem/Biochem; Food industries; Fundamental and applied biological sciences. Psychology; Galactose - metabolism; Hydrolysis; Kluyveromyces - enzymology; Kluyveromyces marxianus var. lactis; lactulose; Lactulose - metabolism; Magnetic Resonance Spectroscopy; Methods. Procedures. Technologies; Molecular Sequence Data; transgalactosylation; transglycosylation; trisaccharides; Trisaccharides - biosynthesis; Trisaccharides - chemistry; β-Galactosidase; transglycosylation; lactulose; β-Galactosidase; trisaccharides; Glycosylases; Enzymatic synthesis; Transglycosylation; Enzyme; Lactulose; Glycosidases; Hydrolases; Identification
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0721343

The enzymatic transgalactosylation during lactulose hydrolysis was studied using the β-galactosidase from Kluyveromyces lactis and an initial lactulose concentration of 250 g/L. During hydrolysis of lactulose, the formation of two novel trisaccharides was followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC−PAD). A maximum trisaccharide yield of 14.05% was observed at 91.9% of lactulose hydrolysis. The two novel trisaccharides obtained by transglycosylation of lactulose were isolated and fully characterized by an extensive nuclear magnetic resonance (NMR) study. Complete structure elucidation and full proton and carbon assignment were carried out using 1D (1H, 13C, and 1D TOCSY) and 2D (gCOSY, TOCSY, ROESY, gHSQC, and gHMBC) NMR experiments. The trisaccharides were shown to be lactulose-based structures; the main one has a Gal unit linked to C-6 of the galactose moiety, and the other one has a Gal unit linked to C-1 of the fructose moiety. Transglycosylation of lactulose allows for the obtention of galacto-oligosaccharides with new glycosidic structures and would open new routes to the synthesis of prebiotics.