Fractional isolation and structural characterization of lignins from oil palm trunk and empty fruit bunch fibers

The lignins from dewaxed oil palm trunk and empty fruit bunch (EFB) fibers were fractionated into 95% ethanol soluble, cold and hot water soluble, and 1% NaOH soluble lignins, respectively. The chemical and structural composi tion of the lignin preparations was determined by using UV, GPC, FT-IR,C-13 -NMR spectroscopy and nitrobenzene oxidation. The alkali soluble and 95% et hanol soluble lignin fractions were found to contain low amounts of chemica lly linked polysaccharides, 2.9-3.9% and 7.5-8.0%, respectively, while the water soluble lignin fractions showed significant amounts of bound polysacc harides (16.2-23.3%). All of the lignin fractions contained a high proporti on of non-condensed syringyl units, together with small amounts of non-cond ensed guaiacyl and fewer p-hydroxyphenyl units. The lignin from oil palm EF B fiber contained a significant amount of esterified p-hydroxybenzoic acid and a minor quantity of esterified glucuronic acid. Trace of ferulic acids was both esterified and etherified to lignin side chains in the EFB fiber c ell walls.