Separation Science and Technology, Vol.42, No.8, 1809-1829, 2007
Fractional separation and structural characterization of chlorophyll and lignin from perennial ryegrass (L-perenne) and cocksfoot grass (D-glomerata)
One chlorophyll rich fraction and two lignin preparations were separated from perennial grass and cocksfoot grass by sequential three-stage treatments with 80% ethanol containing 0.2% NaOH, 2.5% H2O2-0.2% EDTA containing 1.5% NaOH, and 2.5% H2O2-0.2% TAED containing 1.0% NaOH at 75 degrees C for 3 h, respectively, which released 4.6 and 3.6% chlorophyll rich fraction, 2.3 and 5.8%, and 0.9 and 1.0% lignin preparations, except for releasing 8.0 and 10.4%, 79.1 and 77.0%, and 12.9 and 12.5% of the original hemicelluloses, respectively. The lignin fractions obtained from the two different grasses had very similar molecular weights and structural composition. The NMR spectra of the lignin preparations revealed the presence of p-hydroxyphenyl, guaiacyl, and syringyl structures, and the lignin in chlorophyll rich fraction contained more guaiacyl and syringyl units than p- hydroxyphenyl unit, whereas the reverse trend was found in the two lignin preparations. The lignin preparations are distinguished with straw and wood lignins by relatively higher contents of p-hydroxyphenyl unit and lower amounts of condensed units (beta-5 and 5-5 ') and resinol units (beta-beta). This difference in distribution of structural units indicated some structural heterogeneity between grass and straw/or wood lignin.