Background: Barley 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.
Results: Saccharification 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 45 min) during pretreatment at 121 °C. The highest yield of glucose (447 mg g⁻¹) was achieved by pretreatment with 2.0% NaClO+H₂O₂ solution for 30 min, representing an increase of 65.99% compared with untreated barley straw (152 mg g⁻¹). During fermentation, the highest amount of ethanol (207 mg g⁻¹) was obtained under anaerobic plus 0.4 mmol L⁻¹ benzoic acid conditions, representing an increase of 57.49, 38.16 and 10.14% compared with untreated sample (88 mg g⁻¹), aerobic (128 mg g⁻¹) and anaerobic (186 mg g⁻¹) conditions respectively.
Conclusion: The 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.
Keywords: barley straw; fermentation; lignocellulose; pretreatment; saccharification.
© 2014 Society of Chemical Industry.