Steam pretreatment for enzymatic hydrolysis of poplar wood:comparison of optimal conditions with and without SO2 impregnation

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2013

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Steam refining of non-debarked poplar wood with SO impregnation prior to steaming was investigated as pretreatment for enzymatic hydrolysis. Pretreatment conditions were varied in the range of 170°C - 220°C, 3 - 30 min and 0.7 - 2.5 % SO according to a factorial design. Predicted steaming conditions for highest carbohydrate yields after enzymatic hydrolysis were at 200°C, 15 min, and 2.5 % SO. The yield of glucose and xylose from control tests under these conditions was 43 % representing an increase of 9 % compared to results of former experiments without SO impregnation. Investigations on lignin extracted from the fibers revealed no distinct differences between pretreatment with and without SO. No sulfonation occurred by the impregnation with SO. Topochemical analyses of the fibers by cellular UV microspectrophotometry (UMSP) showed an inhomogeneous lignin distribution within the S2 of fibers after pretreatment without SO and local depositions of high UV-absorbing substances in the lumina of fibers and parenchyma cells. The lignin distribution of fiber cell walls after pretreatment with SO was more homogeneous with a preserved fiber network and only little amounts of deposited phenolic compounds in the lumina. Therefore, it might be concluded that the expulsion of lignin hinders the enzymes in accessing the cellulose. Copyright © by Walter de Gruyter • Berlin • Boston.

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Forschungsinformationssystem der UHH

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