Physical and chemical characteristics of pretreated slash pine sawdust influence its enzymatic hydrolysis

Abstract

The aim of this work was to evaluate the effect of different pretreatments applied to industrial slash pine sawdust (Pinus elliottii) on its enzymatic hydrolysis. NREL laboratory analytical procedures for standard biomass analysis were used to characterize the thirty one fibrous materials produced. Eight pretreated materials were selected considering both the chemical composition and the enzymatic hydrolysis yield to further evaluate crystallinity and porosity, determined by X-ray diffraction and thermoporosimetry, respectively. Diluted acid, steam explosion, and slight alkali treatments revealed to be not effective to enhance enzymatic hydrolysis of resinous pines since a maximum yield value of only 25% was achieved. On the contrary, strong alkali treatments promoted the lignin removal, thus increasing the accessibility of the material for enzymatic hydrolysis. In accordance, the highest values of the cellulose crystallinity (about 75–76%) were also obtained. No correlation was found between the porosity and the enzymatic hydrolysis yield. It was concluded that to enhance enzymatic hydrolysis the lignin content of the pretreated material should below. As for the hemicelluloses content, only its interaction with the lignin content is significant, as revealed by the regression model obtained.