Extraction of the wheat straw hemicellulose fraction assisted by commercial endo-xylanases. Role of the accessory enzyme activities

Abstract

Wheat straw is a highly promising raw material for bio-refinery strategies. Most of the literature related to lignocellulose fractionation focuses on cellulose purification and hemicellulose solubilization. Pre-treatments for hemicellulose solubilization without the formation of undesired products usually reach low extraction yields, which leaves an important hemicellulose fraction unused. In this work, we propose a mild process for the efficient extraction of the hemicellulose fraction of wheat straw assisted by partial enzymatic hydrolysis with three commercial endo-xylanase cocktails. A first step with alkali at 40 ºC helped to disrupt the lignocellulosic structure and removed 19% of lignin while maintaining most of the hemicellulose in the solid. The enzymatic step enabled reaching extraction yields of 59.8%, 51.9%, and 42.5% with Ultraflo L, Pentopan mono conc, and Shearzyme 500L, respectively. We also discuss the catalytic properties of each endo-xylanase, in particular, their adscription to the GH10 or GH11 glycosyl hydrolase family, and the relevant role of accessory enzymes.