A synergistic effect of pretreatment on cell wall structural changes in barley straw (Hordeum vulgare L.) for efficient bioethanol production

Abstract

BACKGROUNDBarley straw (Hordeum vulgare L.) is an attractive lignocellulosic material and one of the most abundant renewable resources for fuel ethanol production. Although it has high cellulose and hemicellulose contents, there are several challenges and limitations in the process of converting it to fuel ethanol. High ash, silica and lignin contents in barley straw make it an inferior feedstock for enzymatic hydrolysis. Therefore pretreatment of barley straw could play an important role in inducing structural and compositional changes that increase the efficiency of enzymatic hydrolysis and make the whole process economically viable. RESULTSSaccharification was enhanced using various concentrations (0.0, 0.5, 1.0, 2.0 and 3.0% v/v) of a solution of sodium hypochlorite (NaClO) and hydrogen peroxide (H2O2) and various reaction times (15, 30 and 45min) during pretreatment at 121 degrees C. The highest yield of glucose (447mgg(-1)) was achieved by pretreatment with 2.0% NaClO+H2O2 solution for 30min, representing an increase of 65.99% compared with untreated barley straw (152mgg(-1)). During fermentation, the highest amount of ethanol (207mgg(-1)) was obtained under anaerobic plus 0.4mmolL(-1) benzoic acid conditions, representing an increase of 57.49, 38.16 and 10.14% compared with untreated sample (88mgg(-1)), aerobic (128mgg(-1)) and anaerobic (186mgg(-1)) conditions respectively. CONCLUSIONThe results suggest that pretreatment with 2.0% NaClO+H2O2 solution disrupted the recalcitrant structure of barley straw and enhanced the glucose yield and subsequent bioethanol production. (c) 2014 Society of Chemical Industry