Degradation of veratric acid and other lignin-related aromatic compounds by the white-rot fungus Pycnoporus cinnabarinus

Abstract

Metabolism of veratric acid and other aromatic compounds has been studied in two strains of Pycnoporus cinnabarinus. In non-agitated cultures which contained cellulose as an additional carbon source, veratric acid was demeth(ox)ylated to vanillic acid which accumulated in the medium. Under these conditions, 14CO2 evolution from [4-O14CH3]-veratric acid preceded that from [3-O14CH3]-veratric acid in the case of both strains. 14CO2 evolution was markedly accelerated and increased when 100% oxygen was employed instead of air. Oxygen had not so strong effect on the decarboxylation of 14COOH-labelled vanillic and p-hydroxybenzoic acid but it did increase decarboxylation of 14COOH-labelled veratric acid, indicating the effect of oxygen on the preceding demeth(ox)ylation. There were indications, for example rapid demethylation of veratric acid in early stages of growth when apparent phenol oxidase (laccase) activity was zero, for an existence of a separate demethylase enzyme. However, the participation of phenol oxidases in demeth(ox)ylation cannot be ruled out. Degradation pattern of vanillic acid was basically similar in P. cinnabarinus compared to Sporotrichum pulverulentum (Phanerochaete chrysosporium). Also the effect of carbon source was similar: cellulose as a carbon source enhanced degradation of vanillic acid through methoxyhydroquinone whereas in glucose medium, vanillic acid was reduced to the respective aldehyde and alcohol.