Production of ethanol from sweet sorghum bagasse pretreated with different chemical and physical processes and saccharified with fiber degrading enzymes

The C5 and C6 sugars generated from sweet sorghum bagasse pretreated with five different chemical or physical schemes and then further hydrolyzed with a fibrolytic cocktail were determined. Hydrolysates were fermented with three yeast strains in order to determine which combination generated the highest amount of bioethanol. The bagasse only treated with the enzyme complex generated 50% of the total C5 and C6 sugars available. The pressure-cooked and extruded pretreatments further hydrolyzed with the enzymes generated 17% more sugars compared to the enzyme alone treatment. The enzyme increased the total sugar content in approximately 40% in the three acid pretreated hydrolysates. Among the different pretreatments, only the extrusion process did not generate inhibitors acetic acid, furfural and 5-hydroxymethylfurfural. At 24 h fermentation, the strains Saccharomyces cerevisiae and Issatchenkia orientalis produced, respectively 183.9 and 209.2 mg ethanol/g dry bagasse previously treated with HCl and enzymes.