Characterization of the off-flavor from Pichia pastoris GS115 during the over-expression of a α-L-rhamnosidase.

The off-flavor of Pichia pastoris strains is a negative characteristic of proteins overexpressed with this yeast. In the present study, the P. pastoris GS115 overexpressing a α-L-rhamnosidase was taken as the example to characterize the off-flavor via sensory evaluation, gas chromatography-mass spectrometer (GC-MS), gas chromatography-olfaction (GC-O), and omission test. The result showed the off-flavor was attributed to the strong sweaty note, moderate metallic and plastic notes. Four volatile compounds, i.e. tetramethylpyrazine, 2,4-di-tert-butylphenol, isovaleric acid, and 2-methyl butyric acid were identified to be major contributors to sweaty note. Dodecanol and 2-acetylbutyrolactone were identified to be contributors to the metallic and plastic notes, respectively. It is the first study on the off-flavor of P. pastoris strains, helping understand metabolites with off-flavor of this yeast. Interestingly, it is the first study illustrating 2-acetylbutyrolactone and dodecanol with plastic and metallic notes, providing new information about the aromatic contributors of biological products.