RATIONALE Seventeen different dried yeast strains, including 12 strains of Saccharomyces cerevisiae and five strains of Saccharomyces pastorianus, were analyzed by Direct Analysis in Real Time Time-of-Flight Mass Spectrometry (DART-TOFMS). The resulting mass spectra were used for rapid species and strain differentiation based upon small-molecule metabolomic profiles. METHODS Yeast strains purchased from local shops were suspended in a 1:1 water/methanol solution. Solutions were sampled by dipping the sealed end of melting point capillaries into each vial. Six replicates were measured in positive-ion and negative-ion mode for each strain by using an automated linear rail with the DART source operated with helium gas and a gas heater temperature of 350°C. Averaged and centroided mass spectra were exported for analysis with chemometric software. RESULTS Negative-ion DART mass spectra exhibited less chemical background and more distinctive components than positive-ion DART mass spectra. An on-line search of the Yeast Metabolome Database provided candidate metabolites for selection as features for chemometric analysis. Negative-ion DART mass spectra could distinguish both species and all strains. The DART analysis was also able to identify potential metabolomic differences between top-fermenting and bottom-fermenting yeast, between beer and baking yeast, and between red wine and champagne yeast. CONCLUSIONS All strains could be distinguished by their negative-ion DART mass spectra with 97.7% validation accuracy. Clear differences were observed between dry and liquid forms and Saccharomyces strains with different applications to baking or beverage fermentation. Possible differences in metabolite profiles were suggested, but not confirmed, by accurate mass data.

中文翻译：

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通过实时飞行时间质谱的直接分析，对酿酒酵母和巴氏酵母菌的种类和菌株进行区分。

理由通过实时飞行时间质谱直接分析（DART-TOFMS）分析了17种不同的干酵母菌株，包括12株酿酒酵母和5株巴斯德酵母。所得的质谱用于基于小分子代谢组学谱的快速物种和菌株区分。方法从当地商店购买的酵母菌株悬浮在1：1的水/甲醇溶液中。通过将熔点毛细管的密封端浸入每个小瓶中来取样溶液。使用自动线性导轨，将DART源与氦气一起操作，气体加热器温度为350°C，以正离子和负离子模式对每个菌株进行六次重复测量。导出平均质谱图和质心质谱图，以便使用化学计量软件进行分析。结果负离子DART质谱比正离子DART质谱具有更少的化学背景和更独特的成分。酵母代谢组数据库的在线搜索提供了候选代谢物供选择，作为化学计量学分析的特征。负离子DART质谱可以区分物种和所有菌株。DART分析还能够确定顶级发酵酵母和底部发酵酵母之间，啤酒与烘焙酵母之间以及红酒与香槟酵母之间潜在的代谢组学差异。结论所有菌株都可以通过其负离子DART质谱图进行区分，验证精度为97.7％。干燥形式和液体形式与酿酒酵母菌株在烘烤或饮料发酵中的不同应用之间观察到明显差异。