Submerged cultures of the basidiomycota Cystostereum murrayi emit an intensive coconut-like, sweetish, and buttery smell. For identification of the key aroma compounds, an aroma dilution analysis using dynamic headspace was performed by adjusting the split ratio of the GC inlet system. Flavor dilution (FD) factors varied from 22 up to ≥218, whereby the largest class of compounds represented terpenoids, including two rare stereoisomers of 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran (dill ether, ee ≥ 99.9). By means of nuclear magnetic resonance spectroscopy, the substances with the highest FD factors (29, 212, and 218) were identified as diastereomers of 3,6-dimethyl-3a,4,5,6,7,7a-hexayhydro-3H-1-benzofuran-2-one (dihydromenthofurolactone) and as its corresponding C3-unsaturated lactone. The latter two compounds have not been described for Cystostereum murrayi or for any other basidiomycota previously. Supplementation studies using 2-13C-d-glucose indicated that these lactones as well as the two stereoisomers of dill ether and other terpenoids were formed de novo by the fungus.

Culture supernatants of Basfia succiniciproducens derived from the industrial production of succinic acid exhibit an intense nutty, root vegetable‐like, buttery and sourish smell. By means of headspace‐gas chromatography‐mass spectrometry‐olfactometry (HS‐GC‐MS‐O), 14 odour‐active compounds were perceived and identified using two GC‐columns of different polarity and comparison of retention indices and mass spectra to those of authentic reference compounds. Several alkylated pyrazines, including 2,3,5‐trimethylpyrazine, 5‐ethyl‐2,3‐dimethylpyrazine, 2,3,5,6‐tetramethylpyrazine, 2,3,5‐trimethyl‐6‐ethylpyrazine, 2,3,5‐trimethyl‐6‐propylpyrazine and 2,3,5‐trimethyl‐6‐butylpyrazine were found to contribute to the aroma of the culture supernatant. Quantitation of the pyrazines was performed by means of dynamic headspace‐GC‐MS after standard addition, and 2,3,5,6‐tetramethylpyrazine (9.10 mg/L) was the most abundant compound. Waste streams of the biotechnological production of commodity chemicals may thus represent a sustainable resource for the isolation of aroma compounds.

Among the monoterpenoid aroma compounds formed by the basidiomycete Cystostereum murrayi are highly potent bicyclic benzofuran derivatives. In addition to the dill ethers previously described in a few fungi, two stereoisomers of the rare 3,6-dimethyl-3a,4,5,6,7,7a-hexahydro-3H-1-benzofuran-2-one (1a and 2c), also known as dihydromenthofurolactones, and a C3-unsaturated analogue (3a) are formed by C. murrayi. The analysis of synthesized reference standards of the lactones allowed an unambiguous assignment of the stereoisomers formed by the fungus. Despite a similar structure, two key differences in the stereochemistry of the lactones and dill ethers emerged. The analysis of submerged cultures further revealed the formation of additional, so far unknown, fungal terpenoids, including limonen-10-ol (7) and the corresponding aldehyde limonen-10-al (8). Analysis of chiral terpenoids as well as supplementation studies, including stable isotope-labeled compounds, indicated independent biogenesis pathways for dill ethers and lactones.

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