Insights into exo-Cellulase Inhibition by the Hot Water Hydrolyzates of Rice Straw

Preconditioning of lignocellulosic biomass unfortunately leads to the formation of degradation byproducts that severely inhibit the subsequent enzymatic hydrolysis. This study attempts to prioritize these degradation compounds such that a basis for their mitigation can be developed. Rice straw prehydrolyzates, produced by hot water pretreatment at 220 degrees C and 52 min, were fractionated using centrifugal partition chromatography (CPC) into phenolics, furans, organic acids, monomeric and oligomeric sugars. Purified inhibitors were tested against substrate conversion efficiencies of exo-cellulase enzyme from Hypocrea jecorina. Results showed that rice straw phenolics at 1 g/L reduced the specific hydrolysis rate by 92% compared to that of control. It was followed by acetic acid, which reduced enzyme efficiency by 87% at 1 g/L. The CPC purified xylo-oligosaccharides only inhibited the initial substrate hydrolysis rate of exo-cellulase, that which recovered over time and was comparable to that of the control after 150 min of incubation.