从蔗渣半纤维素水解物发酵液中分离纯化木糖醇

蔗渣半纤维素水解物发酵液必须经过超滤处理,后续的离子交换柱层析过程才能顺利进行。超滤透过液经离子交换柱层析脱盐之后,再经活性炭脱色,这种木糖醇液浓缩至可溶性固形物含量为80%,即可结晶得到含量≥98.5%的木糖醇产品。结晶母液经连续浓缩之后得到的第二次结晶和第三次结晶,则必须经重结晶后才能获得含量≥98.5%的木糖醇产品。从发酵液中的木糖醇到含量≥98.5%结晶木糖醇,产品总收率约为70.6%。本工艺适宜超滤膜的截留分子量为5000kD,阴、阳离子树脂的适宜比例约1.5:1(V/V),活性碳用量为木糖醇溶液可溶性固形物含量的2.5%。当结晶母液中的阿拉伯糖浓度超过木糖醇浓度的45.0%,木糖浓度超过木糖醇浓度的12.6%时,它们都容易与木糖醇一起结晶析出。存在于这种母液中的木糖醇将难于通过结晶的方法而继续得到有效的纯化。

Xylitol Purification from the Fermentative Broth of Sugar Cane Bagasse Hemicellulose Hydrolysate

Ultrafiltration is a necessary process to ensure an efficient operation of the ion-exchange column chromatography of xyolitol fermentation broth of the hemicellulose hydrolysate of sugar cane bagasse. After desalination by ion-exchange column process, followed by decoloration with active carbon, the purified xylitol syrup was concentrated up to soluble solids 80%. Then, the xylitol product could be crystallized out with purity up to 98.5%. The xylitol preparation of the second and third crystallization of the mother liquor could not gain a purity of 98.5% unless it has been recrystallized. In this process, the ultimate yield of xylitol product with a purity of 98.5% could reach about 70.6%. Under this technics, the suitable cut-molecular weight of ultrafiltration membrane is 5000kD and the proper value ratio of anion resin to cation resin is about 1.5:1, while the reasonable dosage of active carbon equals to 2.5 percent of the amount of soluble solids in syrup. In the crystallized mother liquor, if the concentration of arabinose is 45.0% higher than that of xylitol, or the concentration of xylose is 12.6% higher than that of xylitol, this two will crystallize out at same time as the xylitol crystallizs. It is difficult to efficiently purify the xylitol from such mother liquor only by the crystallization process alone.