In these studies Saccharomyces cerevisiae NRRL Y-566 was used to produce ethanol from a concentrated glucose (250-300 g L-1
) solution.
When fermentation media were supplemented with CaCO3 and CaCl2, ethanol concentrations, yield, and productivities were improved
significantly. In control batch fermentation, the culture was able to produce 20.87 g L-1
ethanol with a productivity of 0.25 g L-1 h
-1 when
using 100 g L-1
sugar solution in feed. When supplemented with a solution of 0.40 g L-1 CaCl2, ethanol concentration, yield, and
productivity were improved to 90.0 g L-1
, 0.48, and 1.25 g L-1 h
-1
(500 % increase), respectively. The effect of CaCO3 supplementation was
not as pronounced as that of CaCl2. Using these parameters, the process economics for production of ethanol was performed and it was
projected that supplementation with 0.40 gL-1 CaCl2 would result in the production of ethanol for $0.91 kg-1
. It was also projected that
improving productivity to 37.5 g L-1 h
-1 using cell recycle and supplementation with CaCl2 would result in the production of ethanol for
$0.70 kg-1
employing S. cerevisiae NRRL Y-566. Using Z. mobilis in membrane cell recycle reactors and application of CaCl2 can result in
achieving high productivities (500-600 g L-1 h
-1
) and reduction in ethanol production price to $0.59 kg-1
.
Key words: Ethanol; calcium carbonate and calcium chloride additives; productivity; ethanol yield; cell recycle, process economics
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