Characterization of MWLs from Tamarix ramosissima isolated before and after hydrothermal treatment by spectroscopical and wet chemical methods

Abstract

AbstractTo improve enzymatic hydrolysis, hydrothermal treatment was carried out on the shrubTamarix ramosissima. Milled wood lignin (MWL) was isolated fromT. ramosissimastems before and after hydrothermal treatment, and its chemical structure was characterized by carbohydrate analysis, elemental analysis, methoxy group determination, FT-IR spectroscopy, quantitative13C NMR spectroscopy, 2D heteronuclear single quantum coherence spectroscopy, and gel permeation chromatography. The analyses confirmed thatT. ramosissimaMWL is very rich in syringyl units. It was found that the main reaction responsible for the lignin degradation is the homolytic cleavage of aryl-ether bonds resulting in a reduced amount of β-O-4′ interlinkages and, as a consequence, in elevated amounts of β-β′ and β-5′ linkages. The MWL isolated from the pretreated solid residue was more condensed and had a lower molecular weight than the MWL isolated from untreated material.