| Although Alginate/Chitosan solid core Microcapsule has significant advantages in aspects of the biological cell fermentation but there are still some deficiencies:As the capsule has a solid core within the three-dimensional network structure, making cells more steric hindrance, affecting a large number of cell proliferation, causing bigger mass transfer resistance. Central region of cell microencapsulation can not receive timely discharge of nutrients and metabolites, growth and production of microencapsulated cells decreased. For these deficiencies, in this paper, sodium citrate liquid solid core microcapsules, and alginate/chitosan/alginatesolid liquid core microcapsules be prepared. The preparation conditions were optimized in order to made good mechanical strength liquid core microcapsules. Small molecules through the membrane mass transfer performance and fixed-cell fermentation on cell growth and metabolism were investigation, for the alginate/chitosan/alginate liquid core microencapsulation technology applied in the field of cell culture laid the theory and practice. The main conclusions are as follows:1. By experimental methods and the single factor screening experiment, chitosan film material were modification, obtained by heterogeneous method with a high degree of deacetylation> 90%, oxidation NaNO2 were used to obtaine a series of molecular weight chitosan.2. Single factor experiments were uesd to screen level of Alginate/Chitosan/alginate liquid core microcapsules factors and determined the conditions:chitosan's degree of deacetylation> 90%, the molecular weight of 30000～50000 chitosan, chitosan's pH value of 5.0～6.3, concentration of chitosan is greater than 5.0g/L, reaction time film should be 15 min～30min, pH of sodium citrate is between4.0 and 6.5, liquefaction for more than 20 minutes when liquid core microcapsules with a higher film strength.3. On the base of the single factor experiment,11 influencing factors of the preparation of ACA liquid core microcapsules optimized by response surface methodology experiments. the expansion rate is characterized the film strength and the significant factors were found to determine the optimum conditions. There are three significant factors that depending the strength of the membrane of ACA liquid core microcapsule on the result of Plackett-burman experiment. The there factors are concentration of chitosan, chitosan pH and sodium citrate pH. Determined the center of box-behnken design experiment by the results of steepest ascent experiment and the center conditions are that CHI concentration is 5.5g/L, CHI pH is 6.2 and sodium citrate pH is 5.53.4. Investigate on the transfer properties through the microcapsule membrane of the four kinds of small molecules which are glutamic acid, L-phenylalanine, glucose and lactose. Mass transfer model was established and mass transfer coefficients were fitted as 0.0126,0.0110, 0.0071 and 0.0049. A series of known molecular weight of polyethylene glycol molecules were measured as a model and membrane molecular weight cutoff is measured as 2000.5. The growth and metabolism of the Saccharomyces cerevisiae and E. coli were compared within the environment situation in ACA liquid core microcapsule. The results showed that the growth density and the concentration of metabolites of immobilized Saccharomyces cerevisiae cells in liquid core microcapsules perform better than in the solid core microcapsules and metabolism alcohol concentration remained stable on more batch culture. |
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