Comparative analysis of effect of different immobilization systems with free cells over glucose utilization and ethanol production yield by S. cerevisiae.
An attempt to estimate quantitative effect of different methods of S. cerevisiae immobilization over glucose utilization rate and ethanol yield was made. Yeast cells were immobilized with entrapping the cells in calcium alginate and k-carragenan polymers. The data was compared with that of free cell fermentation. Results from glucose utilization kinetics revealed a marked distinction between free cells and immobilized cells. Free cells initially utilized glucose at a faster rate than the immobilized cells, but this trend is reversed at later stages after 72 hrs. This may be attributed to possible effects of production inhibition of cell activity by ethanol accumulation which is resisted by the immobilized cells. The kinetics of glucose utilization for k-carragenan was quite uniform throughout the process, while in case of sodium alginate it was comparatively lower at first but increased later. Data from ethanol production measurements demonstrated that k-carragenan is more suitable system as compared to sodium alginate encapsulation for getting better yields. The yield of ethanol production was highest in case of carragenan as compared to sodium alginate and least in free cells which can be explained by better resistance to cells from ethanol toxicity in immobilized systems.