Plant-Cell-Wall-Degrading Enzymes Produced by the White-Rot Fungus Ceriporiopsis Subvermispora

The production of various plant-cell-wall-degrading enzymes by the white-rot fungus Ceriporiopsis subvermispora was monitored in shake-flask cultures. Analyses included various cellulolytic (i.e. endo-1,4-b-glucanase, exo-1,4-b-glucanase, 1,4-b-glucosidase), hemicellulolytic (i.e. xylanases, 1,4-b-xylosidases, mannanases, 1,4-b-mannosidases), and ligninolytic (i.e. laccase and manganese peroxidase) enzymes. Other enzymes studied were polyendogalacturonase, proteases, amylases, phenolic acid esterases and lipases. Glucose, cellobiose, avicel and Whatman cellulose were the primary carbon sources used. Other substrates were birch-wood xylan, galacto-mannan and citrus pectin. Ground stems of two fibrous plants, flax and kenaf, were the substrates representing a complete cell-wall composition used. Endo-1,4-b-glucanase and 1,4-b-glucosidase activities were detected in certain culture solutions but, interestingly, no significant amount of exo-1,4-b-glucanase activity was found in cultures of any of the carbon sources. Avicel, in general, gave rise to higher fungal growth and enzyme production compared to the more crystalline Whatman cellulose. Xylanase and mannanase activities were readily detected under all culture conditions used. Flax and kenaf flour generally induced more enzyme production over xylan, mannan and pectin. Laccase and manganese peroxidase were the two ligninolytic enzymes produced. Pectin, xylan and mannan induced more polyendogalacturonase than other substrates. Proteases and amylases were also produced, but no lipase activity was detected. C. subvermispora also produced phenolic acid esterases in the avicel and xylan cultures. Preference for a more amorphous cellulose, avicel and hemicelluloses over a more crystalline Whatman cellulose as substrates for active growth is most likely the reason for the lignin specificity of C. subvermispora. Enzyme profiles suggest that C. subvermispora shows a potential for various industrial applications where removal of the lignin components, while maintaining cellulosic fibre strength property, is important.