Steam explosion and enzymatic pre-treatments as an approach to improve the enzymatic hydrolysis of Eucalyptus globulus

Eucalyptus globulus woodchips were subjected to steam explosion under a variety of operational conditions in order to evaluate their effect on a subsequent enzymatic hydrolysis. Steam explosion enhanced the enzymatic hydrolysis of the solid fraction. The application of a laccase-mediator system (LMS) before the enzymatic hydrolysis increased the glucose yield from 24.7 to 27.1%, probably as a result of the detoxification of the substrate. However, when xylanase was used to boost the LMS treatment, the hydrolysis rates did not improve. In order to assess the total amount of sugars obtainable from E. globulus, the liquid fraction obtained from the steam explosion was subjected to hydrolysis too. The enzymatic hydrolysis of the liquid fraction was more efficient than the acid hydrolysis, breaking down 82.7% of the xylooligosaccharide backbone into its monomeric constituent, xylose. The overall yield was 210 g of sugars per kg of raw material.

► Steam explosion and LMS treatments enhanced the subsequent enzymatic hydrolysis.
► Enzymatic hydrolysis of hemicelluloses-rich liquid fraction yielded 83% xylose yield.
► Severe steam explosion pre-treatments could reduce the hemicelluloses recovery.
► The overall yield of the whole process was 21 g of sugars from 100 g of Eucalyptus globulus.