In addition to cellulose depolymerisation, acid catalysed pretreatments of CGT have lead to near total hemicellulose solubilisation as well as biomass degradation products. The pentose sugars
represent a significant fraction that can either contribute to ethanol fermentations or be exploited for conversion to other products like xylitol or furfural in a biorefinery setting. Likewise, biomass degradation products can impact on both cellulase effectiveness and fermentation productivities and must be minimised as part of the process optimisation (Palmqvist and Hahn-Hägerdal, 2000; Panagiotou and Olsson, 2007). Therefore the investigation was expanded to quantify sugar solubilisation and degradation reaction products during the pretreatment phase. Furthermore, from recovered fibre compositions (Table 3) it is evident that hemicellulose
fractions were completely solubilised, indicating pretreatment conditions for maximising xylose recovery may also be described within the CCD experimental matrix. Quantities of soluble sugars
(xylose and glucose) and the main biomass degradation products, acetic acid, furfural and hydroxymethylfurfural (HMF) in pretreatment liquors are presented in Table 5. Galactans and arabinans were detected in some prehydrolysate liquors at low levels; presumably because they were mostly degraded to their corresponding furans