One step liquefaction,saccharification and fermentation in dry-mill corn ethanol process

    In the typical dry-grind process corn ethanol production, high sugar concentration often occurs at SHF process as well as the initial phase of SSF process, which cause the mash to have a high osmotic pressure resulted in the production during the fermentation process of higher concentrations of glycerol as glycerol aids yeast with osmoadaptation. As a result, the osmotic stress negatively affects yeast performance. One of the technological improvements is to use granular starch-hydrolyzing enzymes during corn liquefaction and saccharification.

Granular starch-hydrolyzing (GSH) enzymes can convert starch into dextrins at temperatures lower than 48 C and hydrolyze dextrins into fermentable sugars during SSF. Therefore, there is no need to heat corn slurry to a higher temperature for liquefaction in the dry-grind process, which allows liquefaction, saccharification, and fermentation steps to be combined into one single step. The advantages are found as follows:

• avoid the increase in viscosity of the corn slurry that occurs during gelatinization and cooking in the conventional process because the rate of glucose production by GSH enzymes parallels the rate of glucose fermentation by yeast
•  yeast cells are subjected to a low osmotic stress due to the low production of glycerol 
•  Low glucose concentration but similar final ethanol concentrations and ethanol yields