Effect of steam explosion pretreatment on pore size and enzymatic hydrolysis of poplar

Abstract

The purpose of this study was to determine the effect of batch steam explosion pretreatment on the rate of subsequent enzymatic hydrolysis of hybrid poplar wood. This pretreatment was found to be effective as indicated by the fact that for many of the pretreatment conditions studied the glucose yield obtained after 24 h of enzymatic hydrolysis using enzymes from Trichoderma reesei And Aspergillus niger is in excess of 90% of the potential, whereas the corresponding yield from unpretreated substrate is only 15%. The effect of pretreatment is believed to be primarily due to the increase in pore surface area accessible to enzyme molecules. Measurements show a considerable increase in pore volume available to 5–9 nm solute probes. Pretreated wood that was subsequently oven-dried hydrolysed poorly and showed a reduction in available pore volume after drying. Xylans are readily hydrolysed to xylose during pretreatment and owing to decomposition the amount of xylose in solution after steam pretreatment decreases as the severity of the reaction conditions increases; the converse is true for glucose. We conclude that steam explosion pretreatment can be effective on hybrid poplar and that the quantitative results obtained can be used for process design.