Studies On Separation And Purification Of Curdlan With Cyclic Ultrafiltration—Solvating Out Crystallization

Curdlan is a neutral extracellular polysaccharide produced by soil microorganism Alcaligenes faecelis var. myxogenes (10C3K), and it has been widespread used in food industry at present.Rheologica properties of curdlan fermentation liquid and separation of curdlan by orthogonal experiments were studied in this paper. Based on range analysis and variance analysis, the concentration of aqueous alkali has significant influence (P<0.05) of extracting rate, aqueous alkali concentration and its pH have dominate effects (P<0.05) on the yield of polysaccharide. On principle of statistical evaluation, these factors that mentioned above, have no dominate effects on nitrogen content at the degree of confidence a =0.05. According to the extraction performance, polysaccharide yield and nitrogen content, the optimized technological condition of extraction is 0.6 mol/L NaOH, 2 hours dissolve, pH 8.0 and 1.5 times of ethanol(95%).The semi-purified curdlan (CUD2) was obtained by removing protein from crude curdlan (CUD1) following the method of Sevag. The separation and purification of CUD2 is the key point of this research, a new technology cyclicultratiltration-solvating out crystallization (CUSOC) was presented by coupling crystallization with membrane filtration. The high-purity curdlan (CUD3) was obtained by choosing the proper technology parameters of CUSOC.The purity of the sample CUD3 was identified by the ultraviolet spectrum and paper chromatography. The result showed that there are no protein, nucleic acid, pigment and mannose within CUD3. Preliminary Studies on the structure of CUD3 by the infrared spectrum and the nuclear magnetic resonance spectrum illuminated that curdlan has D-glycoside linkage,which is the same material with the product of Takeda.