Optimization of Saccharomyces cerevisiae culture in alginate-chitosan-alginate microcapsule

Microencapsulation is one of the promising methods for microorganism immobilization. The parameters of microencapsulation have impact on the growth and performance of microencapsulated microorganism. In this paper, the effects of microcapsules core state (solid or liquid), initial cell density (1.5 × 107, 3 × 106 and 3 × 105 cells/ml of microcapsules), microcapsule diameter (200, 500, 600 and 700 μm) and membrane formation times (0, 5, 15 and 30 min) on cell growth, including proliferating capacity, metabolic activity and product secretion of Saccharomyces cerevisiae, cultured in alginate-chitosan-alginate (ACA) microcapsule, were investigated. The results showed that there was no significant difference in cell growth of microencapsulated cells, whether the core of the microcapsules was solid or liquefied. Increase in inoculate cell density shortened the lag phase time of cell growth, while cell density obtained 25 times of the initial density of 3 × 106 cells/ml of microcapsule, which was the highest. Increase in microcapsules size had no significant impact on cell proliferation, metabolism and product secretion, but the leakage of the bacteria was the least when the microcapsule size was 600 μm in diameter. The increase in membrane formation time reduced the leakage of cells. It was demonstrated that the optimized parameters for microencapsulated S. cerevisiae culture were initial cell density of 3 × 106 cells/ml of microcapsule, microcapsule size of 600 μm in diameter, and membrane formation time of 15 min. This study provides useful information for intestinal delivery of therapeutic agents from genetically modified food-grade microorganisms, using microencapsulation.