The Study Of Natural Polysaccharide Micro-carrier Preparation Technology And The Growth And Metabolism Property Of Microencapsulated Cell

The microencapsulation is an emerging cell immobilization method, the microencapsulated cell culture has good application prospect in fermentation, drugs manufacture, cell transplant, artificial internal organ and other fields. However, there are some problems in the application of microencapsulation, such as the high cost of membrane materials, the complicated preparation procedure, the lower stability and mass diffusion restriction. In order to solve above problems, this paper used natural polysaccharide (Chitosan and sodium alginate) as the micro-carrier preparation materials, the chitosan/alginate microcapsules were prepared by the impulsive electrostatic preparation process. The stability and permeability of chitosan/alginate microcapsules were studied first. Then the growth and metabolism properties of microencaspsulated cell were studied, establishing the theory and the practice foundation for the chitosan/alginate microencapsulation technology in the cell culture domain's application. Experimental results were showed as follow:1. The stability and permeability of chitosan/alginate microcapsules has been systematically studied. The concentration of sodium alginate solution has an important effct on the shape of microcapsules. 20g/L is the best concentration. By increasing the concentration and molecular weight of Chitosan, the stability of microcapsules enhanced, but the permeability reduced. Lengthening properly the membrane formation time, the stability of microcapsules also enhanced. The stability of microcapsules using BaCl₂ and ZnCl₂ as gel solution was better than ones using CaCl₂, but the permeability was worse. Different pH value had a great effect on the stability of microcapsules. The stability of microcapsule in neutral and the acidic environment was better than one in alkalinity environment.2. The microcapsule materials (Chitosan and sodium alginate) have good biocompatibility. The influence of microencapsulation on the prokaryotic cell and eukaryotic cell's growth and metabolism was consistent. Because the microcapsule membrane has certain diffusional resistance to the transmission of substrate and metabolite, compareing with free cell, the growth and metabolism of microencapsulated cell lagged slightly. But the microcapsule can eliminate the substrate inhibition, providing a relative stabile and even micro environment to cell's growth, which making stabilization period of cell growth prolong.3. The substrate consumption rate of the microencapsulated cell speeds up in the batch culture. The maximum cell biomass and the maximum ethanol production in the batch culture were higher than the initial culture and the free culture. The Chitosan/alginate microcapsule has the enough membrane strength, which can withstand the long time fermentation and has good reutilization, suiting in the immobilized cell's high density fermentation.4. The effect of microencapsulation technology on the metabolism of Saccharomyces cerevisiae was studied. The orthogonal experimental results showed that the significant factor was molecular weight of Chitosan. Under the condition that the molecular weight of Chitosan 50,000, concentration of Chitosan 2.0 mg/mL, membrane formation time 15min, the culture medium pH value 6.0, the ethanol output may achieve 13.5g/L, which was higher than one under other conditions.