Brewer´s spent grain to bioethanol through a hybrid saccharification and fermentation process

Brewer´s spent grain, without being pre-treated, has been investigated for bioethanol production through a
Hybrid Saccharification and Fermentation (HSF) process with high solid loading. HSF experiments were
performed in a 2 L bioreactor where Cellic ® CTec2 was used to perform the enzymatic hydrolysis, and
Saccharomyces Cerevisiae was used for the fermentation. The reaction environment was first set to favour
saccharification. Then, after 26 h, the reactor was inoculated with the yeast. The results evidenced the presence
of glucose, xylose, and arabinose after the conversion of cellulose and hemicellulose and a rapid depletion of
glucose after adding the yeast. The pentoses were also consumed, but with a much slower reaction rate. Almost
four hours after adding the yeast, the amount of ethanol had reached a maximum and then began to decrease
as microorganisms began to use ethanol as a substrate after glucose depletion. The obtained ethanol yield,
evaluated with respect to the theoretical value, was equal to 72%.