The Extraction And Biotransformation Of β-glucans From Oat

Oat β-glucan is one kind of non-starch polysaccharide which is usually concentrated in the cell walls of oat. Recently important physiological functions on oat β-glucan have been found out. In this thesis, the optimum parameters for extracting β-glucans from defatted oat bran were determined, the physical and chemical characteristics of the extracts were analyzed, and the biotransformation of oat β-glucan was studied. The results provide valuable reference for the industrialization of oat β-glucan.At first, the spectrophotometric analysis of P-glucans with congo red was established, the accuracy test demonstrated that this method is simple and feasible. And the focus is the optimization of extraction process of p-glucan from oat bran, including extraction temperature, extracting time, pH and solid-solvent ratio. On the basis of single factor experiments, the orthogonal experiment was used to optimize the extracting parameters. The optimum conditions of water extraction were determined:the concentration of NaOH was0.01mol/L, temperature was30℃, reaction time was2hours. And then, oat sovelt-solid ratio was1:25, extraction temperature was80℃, pH was10.0, and extracting time was3hours. Subsequently the extract solution was treated by isoelectric precipitation of protein residue, and precipitation of water-soluble polysaccharids with70%aqueous alcohol. In this condition, the yield of P-glucan was8.28%, the purity was49.79%, and the content of other components in the product were that7.60%moisture,4.27%protein,1.92%ash and0.43%fat.The molecular weight (MW) of β-glucan was determined between9.10×105-1.54×106Da by sepharaose CL-4B gel-filtration column chromatography. The solubility test result is that the solubility of the product becomes higher as the temperature increases. The viscosity experiments proved that, the lower the temperature and the higher the pH are, the greater the viscosity is. However, with the extension of heating time, the viscosity of P-glucan decreases significantly. More than two hours later, no significant changes occur.P-glucan was degraded by the polysaccharide-degrading enzyme, which extracted from the aspergillus niger48s, and the molecular weight of the degraded β-glucan became significantly lower that determinate by gel column chromatography. It indicates that p-glucan molecular weight can be controlled in a range by controlling the reaction conditions of the degradation, in order to make the β-glucan’s characteristics of physiological functions outstanding.The extraction process is simple and feasible, and the product meets the requirements. These demonstrated that it is valuable to the industrial development of oat β-glucan.