Luparia V, Soubeyrand V, Berges T, Julien A, Salmon J-M
Société Lallemand SA, 19 Rue des Briquetiers, B.P. 59, 31703 Blagnac cedex, France.
Appl Microbiol Biotechnol. 2004 Jul;65(1):25-32. doi: 10.1007/s00253-003-1549-3. Epub 2004 Jan 27.
Although yeasts are known to be able to incorporate a wide variety of exogenous sterols under strict anaerobiosis, no data are available on the assimilation of grapevine phytosterols under enological conditions and the eventual impact on fermentation kinetics. We used therefore a mixture of pure phytosterols, in a proportion representative of the different grape skins phytosterols, to supplement a synthetic fermentation medium simulating a grape must. Under anaerobiosis, normal biomass formation was achieved with 5 mg phytosterols l(-1). Similar results were obtained in comparison with the observed maximal fermentation rates. These results clearly indicated that grape phytosterols may efficiently act as a substitute for ergosterol in the yeast membrane for promoting yeast growth and initial fermentative activity. Analysis of total yeast sterols indicated that phytosterols are accumulated without further modification, mainly in their esterified form. However, all the fermentations performed with synthetic media supplemented with phytosterols led to stuck fermentations, linked to a correlative strong decrease in cell viability during the stationary phase. Therefore, grape phytosterols are easily incorporated by yeast cells under enological conditions for promoting initial growth and fermentative activity, but rapidly perturb the yeast membrane properties by being the predominant sterols.
尽管已知酵母在严格厌氧条件下能够摄取多种外源固醇，但关于酿酒条件下酵母对葡萄植物甾醇的同化作用以及对发酵动力学的最终影响，尚无相关数据。因此，我们使用了一种纯植物甾醇混合物，其比例代表了不同葡萄皮中的植物甾醇，来补充模拟葡萄汁的合成发酵培养基。在厌氧条件下，添加5 mg/L植物甾醇可实现正常的生物量形成。与观察到的最大发酵速率相比，得到了类似的结果。这些结果清楚地表明，葡萄植物甾醇可以有效地替代酵母细胞膜中的麦角固醇，以促进酵母生长和初始发酵活性。对酵母总甾醇的分析表明，植物甾醇以酯化形式主要未经进一步修饰就被积累。然而，所有用添加植物甾醇的合成培养基进行的发酵都导致发酵停滞，这与稳定期细胞活力的显著下降相关。因此，在酿酒条件下，葡萄植物甾醇很容易被酵母细胞摄取以促进初始生长和发酵活性，但由于成为主要甾醇而迅速扰乱酵母细胞膜特性。
