Production of volatile compounds in two recombinant P. pastoris strains measured by SPME GC–MS. Strains were fermented for 24 h at 30 °C in 50 mL of brewer’s wort and volatile compound production was subsequently induced with 0.5 % methanol for 12 h. P. pastoris harboring empty vector was fermented under identical conditions with methanol induction as a control. C6-C14 fatty acid methyl/ethyl esters were produced by the two recombinant strains but were not observed in control samples. Amounts of individual volatile compound were shown as percentage of total aromas. Data represents the mean from triplicate experiments ± standard deviation.