IMPORTANCE OF PHENOL OXIDASE ACTIVITY IN LIGNIN DEGRADATION BY WHITE-ROT FUNGUS SPOROTRICHUM-PULVERULENTUM

The lignin degradation abilities of wildtype, a phenol oxidase-less mutant and a phenol oxidase-positive revertant of S. pulverulentum were compared to determine if phenol oxidase activity is necessary for lignin degradation by white-rot fungi. The phenol oxidase-less mutant was unable to degrade kraft lignin or wood. The phenol oxidase-positive revertant regained the ability of the wildtype to degrade kraft lignin and all of the major components of wood. Kraft lignin and lignin-related phenols decreased cellulase and xylanase production by the phenol oxidase-less mutant. Addition of highly purified laccase increased the production of endo-1,4-.beta.-glucanase in the phenol oxidase-less mutant in the presence of vanillic acid and kraft lignin. After addition of laccase to kraft lignin agar plates, the phenol oxidase-less mutant degraded kraft lignin. Phenol oxidase probably functions in regulating the production of lignin- and polysaccharide-degrading enzymes by oxidation of lignin and lignin-related phenols when S. pulverulentum is growing on wood.