High yield of glucose from cassava starch hydrolysis by poly(4-vinylpyridine) hydrochloride

Cassava is an abundant and cheap source of starch which is largely used to produce sugar and dextrin. In this work, Hydrolysis of cassava starch using some active catalysts: poly(4-vinylpyridine) hydrochloride (PVP, HCl), green clay activated with HCl, Amberlyst 36, Montmorillonite KSF, zeolite and HCl were investigated. Temperature, reaction time, concentration of starch and catalyst amount were the parameters considered during each experience. The catalyst precursor (PVP, HCl) showed to be an efficient, selective, recyclable and gave a high yield of glucose syrup (82%) with 95% of total reducing sugar without pretreatment process. Reactions were carried out at 95 degrees C with various concentrations of starch, up to 600 g L-1. The consumable glucose syrup obtained with this process was similar to the commercial reference. A small quantity (2%-3%) of 5-hydroxymethylfurfural (HMF) was the only by-product and it could be extracted with ethyl acetate. Bio-fermentation of the non-treated hydrolysate gave a good yield of ethanol (93%) after only 12 h.