Comparison of atmospheric aqueous glycerol and steam explosion pretreatments of wheat straw for enhanced enzymatic hydrolysis

BACKGROUND: The oversupply of cheap glycerol by the oleochemicals industry together with problems occurring in low-boiling-point organosolv pretreatments, has generated an interest in the use of glycerol in the organosolv pretreatment of lignocellulosic biomass. Atmospheric aqueous glycerol autocatalytic organosolv pretreatment (AAGAOP) is a promising strategy that can effectively enhance enzymatic hydrolysis of lignocellulosic biomass. As a cost-effective technique, steam explosion pretreatment (SEP) is being adopted in industrial applications. Accordingly, work has been carried out to investigate how AAGAOP enhanced enzymatic hydrolysis of lignocellulosic biomass compares with the SEP method. RESULTS: Under controlled laboratory conditions, based on >= 90% cellulose recovery, AAGAOP removed >= 60% hemicellulose and >= 60% lignin from wheat straw while SEP led to similar to 80% hemicellulose and 10% lignin removal. Enzymatic hydrolysis yields of AAGAOP and SEP reached similar to 90% and similar to 70%, respectively. Physical-chemical structural characterization by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), helped explain the above results. The two methods gave priority to dissociating the guaiacyl lignin and had a relatively small effect on syringyl units. However, AAGAOP exhibited a superior performance. CONCLUSION: The two methods enhanced the enzymatic hydrolysis of lignocellulosic biomass by removing and/or altering physical-chemical structural impediments. The AAGAOP technique, with some special advantages, was more effective than SEP in enhancing the recovery and enzymatic digestibility of cellulose. (c) 2008 Society of Chemical Industry.