Enzyme-assisted extraction of hemicelluloses and lignin from organosolv pulps

Wood hemicellulose components, xylan and glucomannan, as well as lignin are interesting starting components for material applications, chemicals and liquid fuels. Thus, efficient and selective separation of these components from wood, pulp or process waters is of interest. With hydrolytic enzymes i.e. hemicellulases and cellulases the different carbohydrate components from lignocellulosic raw materials and pulps can be selectively decomposed. In this study enzymatic treatments were applied to enhance the lignin extraction from organosolv pulps. Organosolv pulps were obtained by cooking wood chips with the Lignofibre (LGF) process with acetic acid and phosphinic acid as catalyst. With the Lignofibre process it is possible to produce lignin rich, strong fibers with high yield. The enzymatic treatments were carried out before alkali extraction of the pulp to enhance the extraction efficiency. The extracted lignin was further isolated by ultrafiltration of the extraction liquor. The effect of enzyme treatment on the quality of the isolated components was assessed by analyzing the molar mass distribution of the isolated fractions using size-exclusion chromatography (SEC). The lignin content of the xylanase treated alkali-extracted pulp was lower than that of the reference pulp indicating that the enzyme treatment enhanced the alkaline extraction of lignin. The xylanase treatment affected also the molar mass distribution of the extracted lignin.