Effect of pretreatment methods on sugar production from hazelnut shells by enzymatic hydrolysis

In this study, different processes (low and high temperature acid and alkali, steam, alkali peroxide, organasolv, ionic liquids and biological) were used for the pretreatment of hazelnut shells and the treated solids further enzymatically hydrolysed to produce glucose. After pretreatments, maximum glucose yield (18.23%) was found with ionic liquid pretreatment ([EMIM]Ac, 1200C, 1/20 solid to liquid ratio, 30 min), followed by alkaline peroxide (15.05%) (2% H2O2 in 2% NaOH, 300C, 1/10 solid to liquid ratio, 6 hr) and high temperature NaOH pretreatment (14.38%) (1800C, 1/5 solid to liquid ratio, 5.25% NaOH, 30 min). 95.46% of glucose was recovered from the raw material after the pretreatment with 1-Ethyl-3-methylimidazolium acetate ([EMIM]Ac). Cellulose-rich and low lignin content raw material obtained with high temperature NaOH pretreatment (1800C, 1/5 solid to liquid ratio, 5.25% NaOH, for 30 min). At these conditions, cellulose content increased from 16,67% to 48.49% and lignin content decreased from 51.10% to 27.28%. Hemicellulose-rich content biomass (17.17%) and lignin–rich content biomass (65.66%) were obtained by organosolv (120 0C, 1/10 solid to liquid ratio, 30 min, 4% NaOH in the 50% EtOH solution) and steam (200 0C, 1/5 solid to liquid ratio, 60 min) pretreatment, respectively. The amount of energy consumed (kJ) per glucose (g) during the pretreatments ranged from 21 kJ/g glucose (alkali peroxide pretreatment) to 3330 kJ/g glucose (ionic liquid pretreatment).