Chemical structure elucidation of total lignins in woods. Part II: Analysis of a fraction of residual wood left after MWL isolation and solubilized in lithium chloride/N,N-dimethylacetamide

Abstract

Abstract The residual wood meal left after extraction of milled wood lignin (MWL) was extracted with lithium chloride/N,N-dimethylacetamide, which is a well-known cellulose solvent, to afford a soluble fraction (cellulose-lignin fraction; CL) in 36.7% yield. The UV elution curve of CL acetate has the same profile as its refractive index (RI) elution curve. After partial degradation of CL by cellulase, the UV elution curve of CL acetate shifted to the low-molecular-mass region in a similar fashion as its RI elution curve. These results indicate that the lignin in CL (CL lignin) is chemically bonded to cellulose. On the other hand, half of the CL lignin was removed by xylanase treatment. It was concluded that approximately half of the CL lignin existed as a lignin-cellulose-xylan complex.