In the case of
the steam explosion, the most marked effect was on the hemicellulose
content, since under the operating conditions and with the
presence of sulfuric acid as catalyst the autohydrolysis of acetyl
groups is favored, decreasing the hemicellulose content in the solid
phase. Besides, it has been reported that this pretreatment also allows
a partial hydrolysis of lignin, through the homolytic cleavage
of b-O-4 ether linkages and other unstable acid moieties, producing
a series of cinnamyl alcohol derivatives and condensation byproducts
[30].