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.

中文翻译：

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α-L-鼠李糖苷酶过度表达期间毕赤酵母 GS115 异味的表征。

毕赤酵母菌株的异味是该酵母过度表达的蛋白质的负面特征。本研究以过表达α-L-鼠李糖苷酶的毕赤酵母GS115为例，通过感官评价、气相色谱-质谱仪（GC-MS）、气相色谱-嗅觉（GC- O），以及遗漏测试。结果显示，异味归因于强烈的汗味、中等的金属和塑料味。四种挥发性化合物，即四甲基吡嗪、2,4-二叔丁基苯酚、异戊酸和2-甲基丁酸被认为是产生汗味的主要因素。十二烷醇和 2-乙酰基丁内酯被确定分别是金属和塑料香气的贡献者。这是首次对巴斯德毕赤酵母菌株的异味进行研究，有助于了解这种酵母的异味代谢物。有趣的是，这是第一项研究表明 2-乙酰基丁内酯和十二醇具有塑料和金属味，提供了有关生物制品芳香成分的新信息。