Hydrolysis is the process by which the lignocellulose polymers are reduced (saccharified) to yield fermentable sugars (hexoses and pentoses) (Harris and DeBolt, 2010). There are two methods of hydrolysis used within the bioenergy and biorefining processes, namely, acid hy­drolysis and enzymatic hydrolysis (Potumarthi et al., 2013, 2012; Dashtban et al., 2009; Ong, 2004).

Acid hydrolysis is the older method of the two and has been implemented on an industrial scale since World War I. In this particular process, dilute or concen­trated acid, normally H2SO4 as it is cheapest, is used to hydrolyze the cellulose with the reaction temperatures dependent upon the molarity; dilute acids require higher temperatures (above 200 ° C) while concentrated acids require lower temperatures. The acid hydrolysis approaches are less attractive due to low yields with dilute acid and the recovery and environmental factors involved with use of concentrated acids (Ong, 2004).

In enzymatic hydrolysis, the lignocellulose is broken down into the corresponding monomeric sugars by spe­cific enzymes produced from bacteria or fungi ( Coyne et al., 2013; Gupta et al., 2013; Ong, 2004; Dashtban et al., 2009). This approach is more complex, expensive and time consuming, in comparison to the acid hydroly­sis approach, but has the advantage of little or no by­products to dispose of at the end of the biorefining process (Ong, 2004) and it can be used for more selective fractionation in a biorefinery context (Menon and Rao, 2012). Pretreatment of lignocelluloses with acid or alkali partially removes the lignin and hemicellulose but also substantially disrupts the fibrillar structure of biomass. Therefore, acid or alkali pretreated lignocellulosic biomass can be saccharified enzymatically to produce fermentable sugars. This results in faster hydrolysis rates and higher glucan enzymatic digestibility. A common belief is that lignin removal in particular promotes faster and more efficient enzymatic cellulose hydrolysis (Zhu et al., 2008).