Evaluation of pretreatment methods for enzymatic saccharification of wheat straw for bioethanol production

► Wheat straw, abundant lignocellulosic feed stock selected for producing ethanol. ► Pretreatment with alkali followed by acid and vice versa for enzyme hydrolysis. ► Pretreatment at low temperature is economically feasible. ► Recovery of maximum sugars by enzymatic hydrolysis for high ethanol yield. Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. The current study is focused on two different pretreatment methods of wheat straw using mild temperatures (100°C for 2h and RT for overnight). In one method, native substrate was treated with 1.5% (w/v) NaOH at two different above mentioned conditions followed by acid hydrolysis (0.75% (v/v) sulfuric acid at 100°C for 2h). In another method, the native substrate was initially treated with acid (0.75% (v/v) sulfuric acid at 100°C for 2h) followed by treatment with 1.5% (w/v) NaOH at two different above conditions. After the pretreatments, the residues were treated with Accellerase 1500 (26U/g) and maximum yield of glucose (65.2gL−1) were found with 0.75% sulfuric acid (100°C for 2h) followed by alkali (1.5% NaOH at 100°C for 2h). Fermentation of this hydrolyzate using Saccharomyces cerevisiae strain produced 24.4gL−1 of ethanol with corresponding yield of 0.44g/g.