|Morrison iii, Wiley|
Submitted to: Proceedings, 1998 American Kenaf Society Conference
Publication Type: Proceedings
Publication Acceptance Date: 9/1/1998
Publication Date: N/A
Citation: Interpretive Summary: Kenaf and flax are bast fibers, which means that they are produced in the cortical regions of the plant stem. Retting, which is the process by which the bast fibers are separated from the non-fiber tissues, is the major limitation to obtaining the fibers for industrial uses. Kenaf and flax vary substantially in the properties and potential uses. Research undertaken in our laboratory showed that kenaf was highly lignified and no easily rettible to ultimate fibers using enzymes. However, flax fibers contain less lignin and barriers to retting and were effectively retted by pectinase-containing enzyme formulations. Research indicated that flax fibers could be obtained by enzymatic retting and indicate potential to develop a new process for supplying a domestic source of linen fiber to US textile industries.
Technical Abstract: Kenaf (Hibiscus cannabinus L.) and flax (Linum usitatissimum L.) are both bast fiber plants. However, substantial variations exist in their structure and chemical composition that determine retting properties and efficiencies. Fiber bundles are in vertical rows in kenaf bast, but in flax bundles occur in a linear row outside the core. Histochemistry and ultraviolet absorption microspectroscopy indicated that kenaf bundles are highly lignified throughout in both the secondary layers and middle lamellae. Middle lamellae contain more lignin than the secondary layers. In contrast, lignin in flax fibers occurs sporadically in middle lamellae and particularly in cell corners. Most of the lignin in kenaf bast is syringyl (syringyl: guaiacyl ratio of ca 8:1), whereas histochemical stains do not indicate this high level of syringyl lignin in flax and suggest mostly guaiacyl lignin. Our results indicated that enzymatic retting of flax, based on highly active pectinases, can degrade the matrix components in flax bundles and thereby produce fine fibers. In contrast, the high lignification in kenaf bast fibers prevents degradation of the fiber bundles per se by retting enzyme mixtures. Instead enzymatic retting using xylanases and cellulases produced clean, highly lignified kenaf fiber bundles in which matrix residue tissues were removed.