ABSTRACT
Vacuum fermentation systems remove fermentation products that are more volatile than water. Because the product to be removed must exert a greater vapor pressure than water, the application of this process is limited to a few compounds. Formic acid is the only organic acid volatile enough to be removed as a vapor. Many alcohols can be removed, although higher alcohols, such as butanols and pentanols, have pure component vapor pressures lower than water, and when dissolved at low concentrations in water, they are more volatile than water. This is due to their longer carbon chains, which increase their liquid-phase activity and thus vapor pressure. Vacuum fermentation has been shown to dramatically increase the productivity of ethanolic fermentations through the removal of ethanol inhibition. By removing ethanol as it is formed, much more highly concentrated feeds can be fermented.
