Chemical and Biological Retting of Kenaf Fibers

The physical and chemical characteristics of fibers after biological, chemical, and enzymatic retting were studied for kenaf cultivated in Jeju, Korea. Retting removes non-fibrous materials leaving separated fibers. Quantitative chemical analyses of kenaf fibers after retting were conducted using gas chromatography—mass spectrometry (GC— MS). Before retting, the syringyl lignin content was 16 mg/g and guaiacyl lignin content was 2.9 mg/g. The syringyl content was reduced by all three retting treatments: bio-retting, chemical retting with NaOH and enzymatic retting with pectinase. Treatment with 3% pectinase decreased the syringyl lignin content to almost one-half that observed in the unretted kenaf and also decreased the guaiacyl lignin content. The ratio of syringyl type lignin/guaiacyl type lignin ranged from 5.8 down to 2.4. Thermogravimetric analysis and differential scanning calorimetry also demonstrated the reduction in non-cellulose content. Viscosity measurements show that the retting processes did not degrade the cellulose polymers of the kenaf fibers.