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

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