Key Laboratory of Systems Bioengineering, Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China.
OMICS. 2010 Oct;14(5):563-74. doi: 10.1089/omi.2010.0016.
Vacuum fermentation is utilized in a wide range of life science industries and biomedical R&D. Little is known, however, on the effects of the vacuum on the yeast, and in particular, on the yeast lipidome that plays a central role in maintaining cell membrane and other vital (yeast) cell functions. The present study evaluated the adaptive responses of Saccharomyces cerevisiae to repeated vacuum fermentation by lipidomic analysis. We employed gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI/MS(n)) to quantify a total of 13 intermediate sterols and 139 phospholipid species of yeast cells. Principal components analysis found that the PI (phosphatidylinositol) 26:0, PI 28:0, PE (phosphatidylethanolamine) 32:1, and PE 34:1 were potential biomarkers to distinguish the vacuum fermentation process. Quantitative analysis showed that vacuum fermentation increased the synthesis of PI and the PC (phosphatidylcholine) species with short saturated acyl chains. The synthesis of PC via CDP-choline and turnover of PC were enhanced, instead of formation via methylation of PE. Additionally, increased PI at the expense of PE and PG (phosphatidylglycerol) was associated with enhancement of ethanol productivity. Vacuum fermentation caused eburicol accumulation, suggesting that vacuum can activate the branch of the ergosterol biosynthesis pathway. Eburicol decrease and PI increase contributed to recovery of cellular activities with oxygenating treatment. Ethanol productivity was increased by sixfold in vacuum-treated cells. These observations may allow the development of future mechanistic approaches to optimization of yeast fermentation under vacuum for bioindustry and life science applications. In particular, our findings on changes in lipid molecular species and the ergosterol biosynthesis pathway elucidate the defense responses of yeast cell membranes during the repeated vacuum fermentation, which by extension, provided an important lead insight on how best to protect the cell membranes from the extreme long-term stress conditions.
真空发酵在广泛的生命科学产业和生物医学研发中得到应用。然而，对于真空对酵母的影响，特别是对在维持细胞膜和其他重要（酵母）细胞功能方面起核心作用的酵母脂质组的影响，人们知之甚少。本研究通过脂质组学分析评估了酿酒酵母对反复真空发酵的适应性反应。我们采用气相色谱-飞行时间质谱联用（GC-TOF-MS）和液相色谱-电喷雾串联质谱（LC-ESI/MS(n)）技术，定量分析了酵母细胞中的 13 种中等甾醇和 139 种磷脂。主成分分析发现，PI（磷脂酰肌醇）26:0、PI 28:0、PE（磷脂乙醇胺）32:1 和 PE 34:1 是区分真空发酵过程的潜在生物标志物。定量分析表明，真空发酵增加了 PI 和短饱和酰基链 PC（磷脂酰胆碱）的合成。通过 CDP-胆碱合成 PC 并促进其周转，而不是通过 PE 甲基化形成 PC。此外，PI 的增加以牺牲 PE 和 PG（磷脂酰甘油）为代价与乙醇生产力的提高有关。真空发酵导致 eburicol 积累，表明真空可以激活麦角甾醇生物合成途径的分支。eburicol 减少和 PI 增加有助于含氧处理后细胞活性的恢复。真空处理细胞的乙醇生产力提高了六倍。这些观察结果可能为未来在真空条件下优化酵母发酵的机制方法提供依据，适用于生物工业和生命科学应用。特别是，我们关于脂质分子种类和麦角甾醇生物合成途径变化的发现阐明了酵母细胞膜在反复真空发酵过程中的防御反应，这也为如何最好地保护细胞膜免受极端长期压力条件的影响提供了重要的见解。
