The white-rot fungus Pleurotus sapidus (PSA) biosynthesizes the bicyclic monoterpenoids 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran (dill ether) (1) and 3,6-dimethyl-3a,4,5,7a-tetrahydro-1-benzofuran-2(3H)-one (wine lactone) (2). Submerged cultures grown in different media were analyzed by gas chromatography-mass spectrometry. The stereochemistry of the formed isomers was elucidated by comparing their retention indices to those of reference compounds by enantioselective multidimensional gas chromatography. The basidiomycete produced the rare (3R,3aR,7aS) and (3S,3aR,7aS) stereoisomers of dill ether and wine lactone. Kinetic analyses of the volatilome and bioprocess parameters revealed that the biosynthesis of the bicyclic monoterpenoids correlated with the availability of the primary carbon source glucose. Spiking the media with 13C-labeled glucose demonstrated that the compounds were produced de novo. Supplementation studies i.a. with isotopically labeled substrates further identified limonene and p-menth-1-en-9-ol as intermediate compounds in the fungal pathways. PSA was able to biotransform all enantiomeric forms of the latter compounds to the respective isomers of dill ether and wine lactone.
Keywords: Pleurotus sapidus; biotransformation; dill ether; isotopic labeling studies; p-menth-1-en-9-ol; submerged cultivation; wine lactone.