Characterisation and hydrothermal processing of corn straw towards the selective fractionation of hemicelluloses

Corn straw was chemically and anatomically characterised. Hydrothermal processing (autohydrolysis) was used for the selective solubilisation of hemicelluloses. The raw material was treated under non-isothermal conditions (150-240 degrees C) and the effects on the composition of both liquid and solid phases were evaluated. The yields and composition of the solid fraction and soluble products are presented and interpreted using the severity factor (log R-0). The operational conditions for the maximum yield of xylo-oligosaccharides (XOS) of 53% of initial xylan, were established for log R-0 of 3.75. Under these conditions 72% of xylan was hydrolysed while cellulose and lignin were not substantially affected although an increase in the enzymatic digestibility of cellulose was attained. For the severest condition (log R-0 =4.51) the solids contained 61.7% glucan and 31.0% lignin. The XOS rich liquors and the glucan and lignin enrichment of the solid phase make corn straw a suitable raw material in a biorefinery framework and the hydrothermal treatment a favourable first step in the processing. (C) 2013 Elsevier B.V. All rights reserved.