Influence of the pretreatment method on the hydrolysis of cassava starch factory residue

Cassava starch factory residue (CSFR) is an attractive lignocellulosic material for bioethanol production because it is one of the most abundant renewable resources. The purpose of this work was to investigate the technical feasibility of converting CSFR into fermentable sugars using 12 different pretreatment methods. The yields of monosaccharides, oligosaccharides, and total sugars present in the hydrolysates obtained from the different pretreatment methods were examined by transferring the solid organic matter present to a liquid phase. We found that pretreatment with a dilute acid was superior to both alkaline and hot water pretreatment methods, while combined chemical-enzymatic pretreatment was superior to single enzymatic pretreatment. More specifically, treatment with a dilute acid was conducive to the formation of monomeric sugars, whereas single enzyme pretreatment and high-temperature alkaline pretreatment methods were conducive to the formation of oligomeric sugars. Pretreatment with 0.5% (w/v) HNO3 (160 degrees C, 10 min) gave the highest total monosaccharide concentration (i.e., 25,827 mg/L) with a yield of 30.99%, whereas hemicellulose (45 U/g CSFR) + cellulose (120 U/g CSFR) pretreatment gave the highest total oligosaccharide concentration (i.e., 22,152 mg/L) with a yield of 26.69%. Finally, pretreatment with 1% (w/v) H2SO4 (121 degrees C, 40 min) + hemicellulose (120 U/g CSFR) + cellulose (120 U/g CSFR) gave the highest total sugar concentration (i.e., 43,196 mg/L) with a yield of 51.84%. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38: 624-629, 2019