Pretreatment of eucalyptus using subcritical CO2for sugar production

Abstract

BACKGROUND Eucalyptus provides a promising feedstock for the bioconversion of lignocellulosic biomass to bio-fuels. Pretreatment of lignocellulosic biomass is an essential step prior to enzymatic hydrolysis to sugars and bioconversion to other useful products. RESULTS In this work, during subcritical CO2 pretreatment, the effects of CO2 pressure, reaction time and temperature on compositional changes and subsequent enzymatic hydrolysis were determined. After the pretreatment of 5 MPa CO2, 80 min and 160 °C, the maximal xylose yield was 9.8 g (including 8.4 g oligomer) based on 100 g native material. When the pretreated eucalyptus were enzymatically hydrolyzed for 60 h, 42.4 g glucose based on 100 g native material could be obtained, representing 92.2% of glucose in eucalyptus. Under the most favourable pretreatment and enzymatic hydrolysis conditions, a maximum total sugar recovery of 50.6 g (including 8.5 g xylose and 42.1 g glucose) based on 100 g native material was obtained, which corresponds to 84.1% yield on the basis of total sugar in eucalyptus biomass. Characterization data were obtained for the pretreated eucalyptus using XRD and SEM analyses. CONCLUSIONS The results suggested that subcritical CO2 pretreatment could enhance enzymatic digestibilities due to the removal of hemicelluloses. © 2014 Society of Chemical Industry