Enhanced cellulose degradation of wheat straw during aqueous ethanol organosolv treatment

Abstract

The degradation of cellulose in wheat straw during aqueous ethanol organosolv (AEO) treatment under different pulping conditions was investigated. For this purpose, molecular weight distribution (MWD) and degree of polymerization (DP) of the resulting cellulose pulp were determined using high performance size exclusion chromatography (HPSEC). The most pronounced effects regarding cellulose degradation were observed when varying the ethanol-to-water ratio. UV detection in HPSEC indicated that residual lignin in wheat straw fibers from organosolv treatments does not occur in free form, but rather is associated with hemicellulose (xylan) and to a minor extent also with cellulose. The established method was suitable for relative comparisons of MWD of variously treated wheat straw fibers and hence for obtaining information regarding the severity of organosolv treatment in terms of cellulose degradation. In summary, AEO treatment at a low ethanol-to-water ratio favours the efficient delignification and removal of xylan from wheat straw, but this occurs at the price of a greatly reduced fiber quality in terms of DP.