The objective of pretreating lignocellusic biomass is to create a reactive substrate for enzymatic hydrolysis increasing ethanol production yields. Birch samples were pretreated by steam explosion and an advanced treatment under different experimental conditions. An organic solvent extraction was performed to remove hemicelluloses, and, to a lesser extent, lignin and cellulose. Chemical analyzes were performed on the extracted fraction and the residual pretreated solids in order to determine the effect of the pretreatment severity on wood composition. The residual solids were subjected to enzymatic hydrolysis to verify the effects of severity on the substrate reactivity. Thermogravimetric analyzes, X-ray diffraction, and gas phase chromatography (GPC) obtained from the samples before and after the pretreatments indicated the structural modifications when the two pretreatment techniques are performed together or separately. Changes in crystallinity and an increase in lignin degradation temperature due to condensation were observed. Also, the results show that as the severity of the pretreatment increases, the amount of insoluble carbohydrates after explosion decrease, and there is a corresponding increase in the amount of organic soluble materials. For samples treated with only steam explosion the sugar conversion reaches 62% of the initial carbohydrate content in wood, and for one of the conditions when the advance treatment is used prior to steam explosion at the same severity 92% of sugar conversion was obtained, representing up to 30% improvement.  The composition of the soluble fraction and solid residues changed with the severity of the pretreatment.

Lignocellulosic chemical and structural changes after combination of two pretreatment techniques and the effects on enzymatic hydrolysis

247th National Meeting (2014)

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