Separation And Purification Of Functional Polysaccharide And Oligosaccharide With Membrane Technology

The natural polysaccharides and oligosaccharides are an important part of functional sugar. The natural polysaccharide and oligosaccharides have great medicinal value and health function, which is quite significant to health of the human beings. Natural polysaccharides were kind of a neutral glucan consisting mainly of linear polymer of maltotriose unites connected by α-(1â†'6) linkages, which mainly included the hyaluronic acid, saliva acid, gellan gum and pullulan, and so on. Natural oligosaccharides were chemical compounds containing 2-10 glycosidic bonds, which were formed by dehydration of monosaccharide hydroxyl and another monosaccharide hydroxyl. So far, the research of natural polysaccharides and oligosaccharides were focused on the production methods. However, the research of separation and purification was much less. In terms of scale and integrated production filed, there are many problems such as smaller production scale, less efficiency, serious environmental pollution, and higher production cost and so on.With development of reverse osmosis, microfiltration, ultrafiltration and nanofiltration membrane, membrane technology was widely applied in the separation and purification field. The wide application of membrane technology provided an environmental technology and economically feasible technology for separation and purification of functional sugar. Therefore, it is necessary to develop a new technology for separation and purification of functional sugar. The separation and purification technology has many advantages, for example large-scale application, environmental protect and efficient production, which broken through the bottleneck of leap-forward development of sugar industry. At present, pullulan and soybean oligosaccharide were typical representative of the function sugar. Amount of researches focused on the pullulan and soybean oligosaccharide production. In this paper, pullulan and soybean oligosaccharide were the research object, and we designed the two kinds of membrane technology for separation and purification of pullulan and soybean oligosaccharide, respectively.(1) Based on the characteristics of pullulan fermentation broth, micro filtration and ultrafiltration membrane, we designed the integrated microfiltration and ultrafiltration membrane technology for separation and purification of pullulan from fermentation broth. In the tests, the operating conditions of microfiltration and ultrafiltration membrane were optimized to give the best separation performance, respectively. Under the optimal operating conditions, the separation and purification performance of the integrated microfiltration and ultrafiltration membrane system was studied with constant diafiltration mode. As a result, pullulan recovery rate could be more than 90% and protein removal rate could be more than 70%. In addition, the fouling of microfiltration and ultrafiltration membrane was investigated. The physical and regular chemistry cleaning method (0.01 mol/L NaOH and 0.01 mol/L HCl) was adopted in the experiments.(2) Based on the characteristics of soybean oligosaccharide and nanofiltration membrane, the paper designed the nanofiltration membrane technology to separation and purification of soybean oligosaccharide. In the experiments, the separation performance of NF-2 was compared with that of the NF-3. At the same time, the operating conditions of nanofiltration membrane in terms of operating pressure, cross-flow velocity, operating pressure and feed concentration were optimized to give the best separation performance. Under the optimal operation conditions, the separation and purification performance of nanofiltration membrane was studied with the constant volume diafiltration mode. As a result, soybean oligosaccharide recovery rate could be more than 80%, which can separate and purify soybean oligosaccharide effectively. In order to reduce membrane fouling, physical and chemical cleaning methods are adopted.(3) In this paper, the tests estimated economic costs of the two membrane technology using the membrane technical manuals and engineering calculation method. The results provide data support for industrial application of the two membrane technology.