Research On Purification Of Galacto-Oligosaccharides

Galacto-oligosaccharide(galactooligosaccharides, GOS) is a functional oligosaccharidesspecial physical and chemical properties as well as peculiar physiological functions. However, galacto-oligosaccharide made by enzymic transgalactosylation reactions has litmited application scope because of its poor purity.This study is aim to find the efficient purification of galacto-oligosaccharides mixture, thus set up a solid foundation for the research and application of galacto-oligosaccharides. Experiments in this research were used to find out the particularlyβ-galactosidase with weak hydrolysis function and strong transglycosylation, the special saccharomyces cerevisiae Hansen with effective mono-saccharides fermentation and to develop a detection method for galacto-oligosaccharides.A detection method for galacto-oligosaccharides was established for the first time: ion chromatography, with four potential pulsed amperometric detectors (E1=+0.10V,E2=-2.00V,E3=+0.60V,E4=-0.10V), using gradient elution method (125mmol/L sodium hydroxide and 2mol/L sodium acetate). This method is proved to effective to complete the detection of 7 types of saccharides in 31minutes, with minimum retention time not less than 0.83 minute.In this research, six kinds of commercialβ-galactosidase were added to lactose solution, and the conversion rate of galacto-oligosaccharides in production was studied later. Lactase Y"Amano"L was selected because of its strong transglycosylation: galacto-oligosaccharides conversion rate was proved to be 43.7% within 4 hour reaction time, and peaks at 46.9% by 48 hours, with 11 types of galacto-oligosaccharides in production.Add four kinds of saccharomyces cerevisiae hansen to galacto-oligosaccharide mixture made by lactase Y"Amano"L and analyze the results with high performance anion exchange chromatography-pulsed amperometric detector (HPAEC-PAD). The results show significant improvement of galacto-oligosaccharide purity, especially when treated by saccharomyces cerevisiae hansen GIM 2.91. Saccharomyces cerevisiae hansen GIM 2.91 raised the purity of galacto-oligosaccharide by 28.48% (from 30.76% to 39.52%), and increased the types of galacto-oligosaccharide in production from 9 to 10. This simple and low cost purification method using saccharomyces cerevisiae hansen offers valuable reference for industrial application of galacto-oligosaccharide.