Fig. 1. Analysis and identification of the hydroxylation of (+)-valencene (sample 1) to β-nootkanol (sample 2) and (+)-nootkatone (sample 3) by different S. cerevisiae strains expressing HPO, CnVO or their mutants, respectively. (A) GC-FID chromatogram patterns of the products obtained by 150 OD₆₀₀ yeast cells incubated with 2 mM (+)-valencene at 30 °C for 18 h. Retention times of (+)-valencene, β-nootkanol and (+)-nootkatone were 14.639 min, 18.349 min and 19.540 min, respectively. Mass spectra of the products are compared with mass patterns of authentic standards (+)-valencene (B), β-nootkatol (C) and (+)-nootkatone (D) standard.