Chemical characterization of lignin and lipid fractions in kenaf bast fibers used for manufacturing high-quality papers

Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, 41080-Seville, Spain; E-mail address: delrio@irnase.csic.es (J.C. del Río)
The chemical composition of lignin and lipids of bast fibers from kenaf (Hibiscus cannabinus) used for high-quality paper pulp production was studied. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of fibers showed a lignin with high syringyl:guaiacyl ratio (5.4) and minor amounts of p-hydroxyphenyl units. Simultaneously, sinapyl and coniferyl acetates were also identified, indicating that this lignin is partially acetylated. p-Hydroxycinnamic acids were only found in trace amounts. The main lipids identified by GC/MS of extracts from kenaf fibers were series of long chain n-fatty acids, waxes, n-alkanes and n-fatty alcohols. Free and esterified sterols and triterpenols, steroid hydrocarbons, steroid and triterpenoid ketones, as well as steryl glycosides were also found. Finally, the fate of the main constituents of kenaf fibers in alkaline pulping was also investigated.
This study has been supported by the Spanish Ministerio de Ciencia y Tecnología (MCyT) and FEDER funds (project AGL2002-00393). A.G. acknowledges a "Ramón y Cajal" contract of the Spanish MCyT. We thank CELESA (Tortosa, Spain) for providing the kenaf and pulp samples, S. Camarero (CIB, CSIC, Madrid) for Klason lignin and hemicellulose analyses and A. T. Martínez (CIB, CSIC, Madrid) for critical reading of the manuscript.