Enzymatic degumming of ramie bast fibers

Bast fibers from ramie (Boehmeria nivea) were treated with cell-free culture supernatants from an Amycolata sp. and a recombinant Streptomyces lividans strain expressing the Amycolata pectate lyase to investigate the degumming effects of different extracellular polysaccharide-degrading enzymes. Culture supernatants from the Amycolata sp. with high pectate lyase activities were most effective in fiber separation and reduced the gum content of ramie fibers by 30% within 15 h. Xylanase activity produced by the Amycolata sp. contributed little to the degumming. Electron micrographs showed that the crude pectate lyase from the Amycolata sp. removed plant gum more efficiently from decorticated ramie bast fibers than the purified enzyme. Similarly, degumming with the crude enzyme of the Amycolata sp. and the recombinant S. lividans strain for 24 h resulted in fibers with a residual gum content of 14.7 and 17.3%, respectively. Degumming with the crude enzyme of the recombinant Streptomyces strain was slightly improved by the addition of a commercial pectinesterase. No significant degumming was observed with the crude enzyme from an S. lividans strain that did not produce the Amycolata pectate lyase. These results indicate that the pectinolytic activity of the Amycolata sp. plays an active role in degumming of ramie bast fibers.