Ethanol, fermentation advantages

The advantageous use of membranes in the removal of toxic compoimds produced during fermentation has been demonstrated in several fermentation systems. Increased (2.5 fold) volumetric productivities and product concentration yields (fourfold) were reported by Christen et al. [209] in ethanolic fermentations assisted by supported hquid membranes. Increased final product concentrations and yield were also reported by Xavier et al. [134] when comparing membrane-assisted extractive fermentation of lactic acid with conventional fermentations. 

Ethanol production depends not only on the sugar yield, but also on the fermentability of the solution. To investigate the fermentability of the pretreated com stover, fermentations were performed with baker s yeast. Baker s yeast has often been proposed as the best organism for the fermentation of lignocellulosic hydrolysates (28,29) and has the advantages that it is quite robust and was found to be less sensitive to inhibitors than cultivated yeast (30,31). 

The catalytic dehydration of ethanol to ethylene in SC water may be commercially important (16). Although high quality commercial alumina catalysts exist for the vapor phase dehydration of ethanol, the commercial processes require the ethanol feedstock to be relatively free of water. Hence the ethanol must be distilled from the ethanol-water mixture which is the product of fermentation processes. By avoiding this distillation step, and securing phase separation of the ethylene product from the ethanol-water reactant, SC dehydration of ethanol could enjoy advantages over existing commercial technologies. 

---