VANILLIN AS A PRODUCT OF FERULIC ACID BIOTRANSFORMATION BY THE WHITE-ROT FUNGUS PYCNOPORUS-CINNABARINUS-I-937 - IDENTIFICATION OF METABOLIC PATHWAYS

Ferulic acid metabolism was studied in cultures of the white-rot fungus Pycnoporus cinnabarinus I-937. After 6 days of growth, during the secondary metabolism of the fungus, the concentration of vanillin in the culture medium reached a maximum of 64 mg l(-1), corresponding to a molar yield of 27.5%. During the biotransformation process, the propenoic side chain of ferulic acid was oxidatively cleaved to yield vanillic acid, further decarboxylated to 2-methoxyhydroquinone. In addition, two reductive routes were evidenced, involving the conversion of ferulic and vanillic acids into coniferyl and vanillyl alcohols, respectively. The biotransformation process was not easily controlled since the P. cinnabarinus species is known to release laccase into the growth medium. When produced, the enzyme countered the vanillin formation by promoting the polymerization of ferulic acid into lignin-like polymers.