Performance of repeated fermentation using recycled immobilized yeast.

Saccharomyces cerevisiae was embedded by 2.5%(w/v) sodium alginate and 2%(w/v) calcium chloride at the yeast concentration of 2%(w/v, dry cells). The immobilized yeast was employed to produce ethanol continuously in repeated batch fermentation system. In order to slow down the performance degradation of immobilized yeast cells, regulation of their fermentation capability was conducted through Yeast Extract Peptone Dextrose(YEPD) medium activated. Additionally, the structure of immobilized particles and the distribution of yeast cells were characterized by Scanning Electron Microscope(SEM). The immobilized beads fermentation performance was significant improved after regulated. The experiment was carried out with the condition of pH 4.0, 35℃ when the glucose concentration was 80g/L. the experiment results showed: before regulated, the mean value of ethanol volumetric productivity was 0.33g/(L·h) in three sequential fermentation cycles; after regulated, the fermentation time of each batch was shorted from 72h to 24h, the mean value of ethanol volumetric productivity was 1.22g/(L·h) in five sequential fermentation cycles.