Continuous and static fermentation of glucose to ethanol by immobilized Saccharomyces cerevisiae cells of different ages

Glucose was converted to ethanol by calcium-alginate-entrapped Saccharomyces cerevisiae NRRL Y-2034 cells that were 24, 48, 72, and 96 h old in continuous-flow and static repeated-batch fermentors. In general, older yeast cells were more efficient than younger ones. In most cases, the continuous fermentations were better than the static ones in producing maximum ethanol yields (5.11 g/10 g of glucose) over extended time periods. The best static fermentation (with 24-h-old cells) converted 100% of the glucose to ethanol for about 12 days, whereas the best continuous fermentation (with 96-h-old cells) converted 100% of the glucose for a remarkable period of about 3 months.