Laboratory of Forest Resources Management, Division of Forest Ecosphere Management, Department of Forest and Forest Products Sciences, Kyushu University
九州大学大学院農学研究院森林資源科学部門森林生産制御学分野
The decomposition of vanillic and benzylvanillic acids labeled with $^{14}$C either at carboxyl, methoxyl, or aromatic ring was studied during the 10-day cultivation of Phlebia radiata. Seventy percents of carbon dioxide evolved from carboxyl-labeled vanillate and about 40% from ring carbon-labeled vanillate and carboxyl-labeled benzylvanillate. The degradation of methoxyl group from vanillic and benzylvanillic acids reached a similar level, yielding about 25% after one week growth of P. radiata in these conditions. The radioactivity inside mycelium reached two maximas, the first on the 2nd-3rd day after the induction and the second on the 7th day after the induction. The first peak could be derived from high polymerization which can accompany high laccase activity. These polymers of decarboxylated quinones probably attach themselves to the mycelium and can be subsequently degraded by the P. radiata extracellular enzymatic system. These enzymes can demethylate monomeric and polymeric structures as well as cleave the aromatic ring. The late second peak inside the mycelium can be attributed to the cleavage of monomers originating from the degradation of polyquinones or from the secondary metabolites.