. Predictions generated from the quadratic equation to describe the effect of pretreatment temperature and acid concentration on glucose recoveries following enzymatic hydrolysis are
shown in Fig. 1. It is evident that at low acid concentrations glucose recovery increases significantly with an increase in temperature and then follows a smooth decline at higher temperature settings.Similarly, increasing acid concentrations significantly influenced enzyme catalysed glucose recoveries. The response surfaces exhibit similar sensitivities to both temperature and acid concentrations and the terms x2 and x3 displayed similarly weighted coefficient values of 19.09 and 22.04 respectively (Table 4). In related optimisation studies, enzymatic hydrolysis of pretreated eucalyptus wood was significantly influenced by increasing pretreatment temperature followed by acid strength and to a lesser degree reaction holding times (McIntosh et al., 2012). Avci et al. (2013) used a similar composite design when pretreating corn stover with phosphoric acid and reported that glucose yields were largely sensitive to
increasing pretreatment temperature, more so than acid loadings. Residence times can and do influence the enzymatic release of glucose particularly under very mild and extreme pretreatment conditions.