论文总字数：14708字

摘 要

右旋糖酐在医疗领域，食品领域具有广泛的用途，现有以蔗糖为底物生物法制备右旋糖酐的工艺，此工艺会副产大量的果糖，果糖在医疗食品领域同样有广泛的用途。为了提高右旋糖酐制备工艺的经济效益，对副产果糖进行提纯浓缩结晶，实验中以纳滤膜将果糖从以蔗糖-果糖体系为主的溶液中分离出来，考察了操作压力对纳滤性能的影响，在一定范围内，压力的增长与体积通量的增加呈递增关系，其分离通量可达到87.5 L·m²/h。随着压力的升高，果糖和蔗糖的透过率均有所下降，但在0.8 Mpa下仍分别达到81.0%和19.4%，说明纳滤膜可将绝大部分蔗糖与果糖分离。对果糖结晶的工艺进行了优化，首先绘制了三种不同比例的乙醇溶剂下的温度-溶解度曲线，确定将结晶温度控制为15℃。随后考究了晶种添加量对结晶收率的影响，当晶种添加量为2%，果糖收率可达44.3%。第三，研究了养晶时间和降温方式对结晶收率的影响，发现梯度降温对结晶收率无显著影响，养晶12h，即可完成结晶。基于以上研究优化后的工艺条件，果糖的结晶收率为50.86%。本研究为提高右旋糖酐工艺经济效益提供了参考价值与借鉴意义。

关键词：右旋糖酐，蔗糖，果糖，纳滤膜，结晶

Recovery of fructose during dextran extraction

ABSTRACT

Dextran has a wide range in medicine, in food. The existing process of preparing dextran with sucrose as the substrate can produce a large amount of fructose, which is also widely used in the field of medical food. In order to improve the economic benefits of the preparation process of dextran, the by-product fructose was purified, concentrated and crystallized. In the experiment, fructose was separated from sucrose - fructose solution by nanofiltration membrane, and the effect of pressure on the performance of nanofiltration was examined. Within a certain range, there is an increasing relationship between pressure increase and volume flux increase, and the separation flux can reach 87.5 L·m2/h. With the increase of pressure, the transmittance of fructose and sucrose decreased, but still reached 81.0% and 19.4% respectively under 0.8mpa, indicating that most sucrose and fructose could be separated by nanofiltration membrane. I also try to optimized a part of the techbology of fructose crystallization. First, the temperature-solubility curves of three different water-ethanol mixed solvents were plotted, and the end point of crystallization was determined to be 15℃.Second, the effect of seed addition amount on crystal yield was studied. Then the effect of seed amount on crystallization yield was studied. When seed amount was 2%, the yield of fructose reached 44.3%. Thirdly, the effect of crystallization time on crystallization rate was studied. Clear gradient cooling has no significant effect on crystallization yield.The results showed that fructose could be crystallized in 12 hours. Based on the above studies, the crystallization rate of fructose after optimization was 50.86%.This study provides reference value and significance for improving economic benefits of dextran process.

Key words： dextran, sucrose, fructose, nanofiltration membrane ,crystallization

目 录

摘 要Ⅰ

ABSTRACTⅡ

第一章 文献综述1

1.1 研究背景1

1.2 分离果糖的方法1

1.2.1 浓缩-浓缩2

1.2.2 结晶技术3

1.2.3 果糖结晶相关4

1.3 本课题研究的目的与意义5

1.4 本课题研究的主要内容5

第二章 材料与方法6

2.1 实验材料与设备6

2.1.1 主要材料与试剂6

2.1.2 实验设备6

2.2 实验方法6

2.2.1 操作压力对纳滤膜分离性能的影响7

2.2.2 不同乙醇溶液比例为溶剂的果糖溶解度曲线的绘制7

2.2.3 结晶收率7

2.2.4 结晶流程7

2.2.5 晶种添加量对果糖结晶的影响7

2.2.6 养晶时间对果糖结晶的影响8

2.2.7 降温速率对结晶的影响8

第三章 结果与分析9

3.1 纳滤膜分离9

3.1.1 压力对纳滤膜纳滤性能的影响9

3.2 果糖结晶11

3.2.1 溶解度曲线的测定11

3.2.2 晶种添加量对果糖结晶的影响14

3.2.3 养晶时间对果糖结晶的影响15

3.2.4 降温速率对果糖结晶的影响16

第四章 结论与展望18

4.1结论18

4.2展望18

参考文献19

致谢20

第一章 文献综述

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