Dilute phosphoric acid pretreatment of corncobs for biofuels production

Abstract

A waste product from corn production, corncob, is one type of lignocellulosic material, which is a new targeted source of fermentable carbohydrates that can be converted into second generation biofuels. In order to convert corncob to biofuels, the first problem that must be solved is that the structure of corncob limits the extent to which enzymatic hydrolysis of polysaccharides into sugar can occur. Therefore, a pretreatment process is an essential step to remove hemicelluloses and break down cellulose crystallinity to amorphous form prior to the enzymatic hydrolysis process, and enhance cellulose accessibility in the hydrolysis step. Various conditions in the pretreatment process, such as temperature, time, acid concentration, and liquid-to-solid ratio were investigated to determine optimum conditions. After pretreatment, a high yield of 27.62 g/L total sugar was obtained under optimal conditions of 140 °C, 10 min pretreatment time, 2 % (w/w) H3PO4 at a 10:1 liquid-to-solid (LSR) ratio. The total sugar yield of 46.14 g/L was obtained with the two-stage process (pretreatment and enzymatic hydrolysis).