Resumen de Study of galacto-oligosaccharide formation from lactose using Pectinex Ultra SP-L
Alejandra Cardelle Cobas, Mar Villamiel, Agustín Olano, Nieves Corzo Sánchez
BACKGROUND:Galacto-oligosaccharides (GOS) are synthesised from lactose by transglycosylation using β-galactosidase (EC 3.2.1.23) and are recognised as prebiotics. The commercial enzyme preparation Pectinex Ultra SP-L produced by Aspergillus aculeatus possesses β-galactosidase activity; however, because its use has been directed towards the formation of 6′-β-galactosyl-lactose, no data have been reported on the formation of other GOS. Since the composition of the oligosaccharide mixture obtained during lactose hydrolysis may affect the prebiotic properties, in this study the influence of various parameters (pH, temperature, time and enzyme and lactose concentrations) on the formation of GOS using Pectinex Ultra SP-L was investigated. RESULTS:High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) analysis allowed the detection of disaccharides other than lactose, trisaccharides and minor amounts of higher-molecular-weight GOS. The main GOS formed were a trisaccharide identified as β-D-Galp-(1 → 6)-Lac (6′-β-galactosyl-lactose) and a disaccharide identified as β-D-Galp-(1 → 6)-D-Gal (galactobiose). Other GOS detected were tentatively identified as β-D-Galp-(1 → 6)-D-Glc (allolactose), β-D-Galp-(1 → 3)-D-Glc and β-D-Galp-(1 → 3)-Lac. Trisaccharide formation was favoured by a pH increase from 4.5 to 6.5, whereas the disaccharide content increased as the pH decreased, reaching a level of 11% at pH 4.5. 6′-β-Galactosyl-lactose production increased gradually with increasing temperature, attaining a maximum value of 17% at 60 °C after 7 h, whereas disaccharide formation was optimal at 50 °C, reaching a level of 10% after 24 h. CONCLUSION:The results indicate that Pectinex Ultra SP-L can be used to obtain GOS mixtures of different composition depending on the operating conditions. It has been shown for the first time that Pectinex Ultra SP-L can be used for the selective formation of disaccharides. Copyright © 2008 Society of Chemical Industry
