Rapid Recovery of Fermentable Sugars for Biofuel Production from Enzymatic Hydrolysis of Microcrystalline Cellulose by Hot-Compressed Water Pretreatment

Abstract

Enzymatic hydrolysis of microcrystalline cellulose is a multistep heterogeneous reaction limited by the initial action of enzyme to produce short glucose chains, due to the presence of strong intermolecular and intramolecular hydrogen bonding networks in cellulose chains. The results in this study show that enzymatic hydrolysis of the liquid product from hot-compressed water (HCW) pretreatment of microcrystalline cellulose can be immediately converted into glucose oligomers with DPs up to 5 without incubation even at a low enzyme loading (i.e., ~8.6 FPU/g glucan-equivalent). A high enzyme loading (i.e., ~140 FPU/g glucan-equivalent) is able to convert all the glucose oligomers into glucose and cellobiose after 1 h incubation. Overall, the sugar recovery after HCW pretreatment can be drastically increased by up to 2 orders of magnitude, depending on enzyme loading and incubation time. Therefore, HCW pretreatment of microcrystalline cellulose is an effective pretreatment method to break hydrogen bonding networks and convert crystalline bundles of long cellulose chains into soluble glucose oligomers with a wide range of degrees of polymerization (DPs), drastically increasing the chain ends accessibility and enabling enzymatic hydrolysis to take place homogeneously.