Effects of different acid hydrolyses on the conversion of sweet sorghum bagasse into C5 and C6 sugars and yeast inhibitors using response surface methodology

Two different diluted acid pretreatments (sulfuric and hydrochloric acid) and one mixture of these acids were tested in sweet sorghum bagasse and analyzed through surface response methodologies. The response variables were C5 and C6 sugars and inhibitors (acetic acid, 5-hydroxymethylfurfural, and furfural). Results indicated that the three different pretreatments yielded similar amounts of total potentially fermentable sugars. The proposed acid hydrolysis schemes liberated 56–57% of total sugars available in the sweet sorghum bagasse (390–415 mg sugar/g bagasse) and 44–61 mg total inhibitors/g bagasse. A mild detoxification was effectively used in the optimized hydrolysates, but did not have effect an effect in the HCl/H2SO4 mixture. The acetic acid and HMF significantly decreased in the HCl and H2SO4 detoxified hydrolysates without any significant degradation of sugars. The HCl treatment was a good alternative due to its relatively lower hydrolysis time and adequate generation of C5 and C6 fermentable sugars.