Synergetic Physical Freezing and Chemical Pretreatment of Lignocellulosic Sugarcane Bagasse Followed by Enzymatic Hydrolysis

Abstract

This study focuses on employing an eco-friendly pretreatment approach for lignocellulosic Sugarcane Bagasse (SCB) as a major problematic solid waste in Egypt, complying with the standard legislation as well. The applied technique depended on SCB physical fractionation via freezing, followed by chemical hydrolysis using alkaline hydrogen peroxide (AHP) and enzymatic hydrolysis. The changes occurred in macrostructure and the entire lignocellulosic compounds during the pretreatment stages were evaluated. Freezing fractionation resulted in relatively low glucose yield and saccharification ratio at -20°C for 2 h of 307.52 mg/gm native SCB and 48.5%, respectively, where no total reducing sugars (TRS) was obtained. Further AHP pretreatment was performed for the frozen-fractionated SCB at -20°C and 2 h with assistance of Box–Behnken Design response surface methodology (RSM). The investigated key parameters were H2O2 concentration (3, 5.5 and 8 %v/v), temperature (25, 42.5 and 60°C) and pretreatment duration (1, 3 and 5 h). The results revealed that the statistical modelling was able to predict the response of glucose yield and TRS production with R2 = 0.8221 and 0.8814, respectively. Applying the optimization tool of RSM, the optimum predicted values of glucose yield and TRS production were (886.51 mg/gm native SCB and 1.44 mg/mL), respectively; confirmed by the experimental analysis (898.5 mg/gm native SCB and 1.32 mg/mL), respectively. The coincided saccharification ratio was 97.5%. These results were obtained at H2O2 of 3 % (v/v), 56.93°C and 1 h which were 4.32 and 2.01 times higher than that obtained during the freezing pretreatment phase for glucose yield and saccharification ratio, respectively.