After the hydrolysis
the mash is inoculated with yeast and subjected to ethanol fermentation.
This kind of process is named separate hydrolysis and fermentation
(SHF). The enzymatic pretreatment is a costly process
because the liquefaction step is conducted in high temperature
(80–100 C) what demands large amount of energy, also the saccharification
step is costly because glucoamylase acts slowly and
optimal temperature for its activity is ca. 50–60 C. The optimization
for energy demand for starch hydrolysis for ethanol production
led to development of simultaneous saccharification and
fermentation (SSF) process, in which liquefied starch slurry is
cooled to temperature where yeast are able to ferment and glucoamylase
is added so the sacchrification of dextrins and utilization
of resulting monomeric sugars occurs at the same time