Isolation and Fractional Characterization of Ball-Milled and Enzyme Lignins from Oil Palm Trunk

Ball-milled and enzyme lignins were isolated from the trunks of oil palms and subsequently studied. The lignins were fractionated into pure milled lignin (PML), pure enzyme lignin (PEL), lignin rich enzyme lignin (LREL), hemicellulose rich milled lignin (HRML), and solubilized lignin obtained during enzyme treatment (SLET) fractions by a two-step precipitation method. The chemical and structural composition of the five lignin preparations was determined by using UV, GPC, FT-IR, (13)C NMR spectroscopy and nitrobenzene oxidation. Pure milled lignin and pure enzyme lignin fractions were found to contain rather low amounts of neutral sugars, 2.2-3.1%. The lignin fractions contained a high proportion of noncondensed syringyl units with small amounts of noncondensed guaiacyl and p-hydroxyphenyl units. Trace amounts of p-coumaric and ferulic acids were also found to be associated with lignin in the oil palm trunk cell walls.