Abstract: The purpose of this study was to investigate the effect of Aspergillus nigerus, Mucor sp. and Yarrowia lipolytica on the conversion of valeneene to nootkatone using solid phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS). The results showed that all these three strains were capable of transforming valencene to nootkatone. Other products, such as α-terpinol and D-carvone, were also found during the biotransformation. The highest amount of nootkatone was found to be produced by Yarrowia lipolytica with a yield of (252.52 ± 15.79) mg/L and conversion rate of (27.45 ± 1.72)% followed by A. niger and Mucor sp. The amounts generated by the latter two strains were (140.94 ± 30.26) and (137.67 ± 14.02) mg/L, and the conversion rates were (15.32 ± 3.29)% and (15.45 ± 3.36)%, respectively. Using an orthogonal array design the optimal fermentation medium for Y. lipolytica was determined to consist of lactose 40 g/L, peptone 15 g/L, and FeSO4·7H2O 0.6 g/L. Using the optimized culture medium, the yield of nootkatone was up to (457.32 ± 76.11) mg/L, and the conversion rate was 49%, which increased by 21.55% compared to that before optimization.

Key words: valencene, nootkatone, biotransformation