Whole-Cell Fungal Biotransformation of para-Hydroxycinnamic Acids Mediated by Phenolic Acid Decarboxylase, Carboxylic Acid Reductase and Alcohol Dehydrogenase

Microbial biotransformation of para-hydroxycinnamic acids (pHCAs) such as para-coumaric, caffeic, ferulic and sinapic acids into vinylphenols is catalyzed by phenolic acid decarboxylases (PADs), while reduction to their corresponding aldehydes and alcohols is mediated by carboxylic acid reductases (CARs) and alcohol dehydrogenases (ADHs), respectively. The present study systematically evaluated a diverse set of endophytic and basidiomycetes fungi as whole-cell biocatalysts for the transformation of pHCAs into their corresponding vinylphenols and/or aldehydes and alcohols. Twenty-three fungal strains were screened for their PAD, CAR and ADH activities. Based on ultra-high-performance liquid chromatography–diode array detector (UHPLC-DAD) analysis, fourteen strains were selected for preparative-scale biotransformations across all four substrates. Previous literature largely emphasizes enzyme activity or single substrates, seldom covering all four pHCAs. The strain Umbelopsis sp. JAR-T demonstrated promising biotransformation of para-coumaric acid and ferulic acid to 4-vinylphenol (28% isolated yield) and 4-vinylguaiacol (40% isolated yield), respectively, with minimal by-product formation. The results highlight endophytic fungi as largely untapped and versatile biocatalysts for pHCA biotransformation and establish whole-cell fungal systems as robust, non-recombinant alternatives to engineered platforms. This integrated screening-to-preparative workflow provides a scalable framework for the production of value-added compounds with potential applications in the food, cosmetic and pharmaceutical industries.