Suitable conversion technologies are needed in order to effectively breakdown or deconstruct biomass into simple sugars, carbohydrate derivatives or bio-oils that are more easily converted into fuels in combination with downstream conversion technologies to subse­quently upgrade these intermediates into bioenergy, biofuels and value-added bioproducts.

At present, the bioconversion of lignocellulose is carried out in four major steps viz. pretreatment, hydro­lysis, fermentation and separation/purification to recover bioenergy/biofuels and residues (more recently, the recovery of coproducts has becoming increasingly important). The pretreatment of lignocellulose materials is considered a key step in bioenergy production and indeed in biorefining as it accelerates the hydrolysis pro­cedure, by enhancing cellulose accessibility and increasing pore size, which, in theory, leads to higher sugar yields for fermentation. An ideal pretreatment should remove lignin and thus reduce the crystallinity of cellulose (Lynd et al., 2002), increase porosity and accessibility of the cellulose (and hemicellulose) to enzymatic hydrolysis, release/generate low levels of inhibitory compounds, be low cost and have low energy requirements. The overall result should be a reduction in the recalcitrance of lignocellulose and an increase in accessibility to enzymes.

In general, accessibility of cellulose is achieved through the removal of lignin and hemicellulose polymers through various pretreatment methods, which can be defined as chemical, physical or biological (O’Donovan et al., 2013; Dashtban et al., 2009; Taherzadeh and Karimi, 2008; Ong, 2004; Howard et al., 2003).