초록
The dissolved carbon dioxide (DCO<SUB>2</SUB>) evolved from Saccharomyces cerevisiae was measured for the duration of very-high-gravity (VHG) ethanol fermentation conducted at four glucose feeds (150, 200+/-0.21, 250+/-0.12, and 300+/-0.28g/L). The DCO<SUB>2</SUB> concentration profiles depict evolution patterns that depend on the extent of glucose utilized. A mass balance for DCO<SUB>2</SUB> was proposed by taking into account the physiochemical behavior of CO<SUB>2</SUB> and biological processes occurring under VHG ethanol fermentation conditions. The proposed equations could interpret the underlying CO<SUB>2</SUB> desorption, CO<SUB>2</SUB> conversion, and CO<SUB>2</SUB> evolution on the basis of yeast activity during VHG ethanol fermentation. Consequently for 150 and 200+/-0.21gglucose/L absence of yeast activity was interpreted in terms of zero CO<SUB>2</SUB> evolution rate (CER(t)). In contrast, under 250+/-0.12 and 300+/-0.28gglucose/L conditions the presence of non-zero residual glucose resulted in non-zero CER(t). The mass balance equation could also interpret that the physical desorption of CO<SUB>2</SUB> from the fermentation broth did not follow the equilibrium relation between dissolved and off-gas CO<SUB>2</SUB> concentrations as defined by Henry's law under current experimental conditions.