Sucrose fermentation by Saccharomyces cerevisiae lacking hexose transport
Sucrose fermentation by Saccharomyces cerevisiae lacking hexose transport
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DOI：
10.1159/000082078
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发表时间：
2004-01-01
影响因子：
1.2
通讯作者：
Stambuk, BU
中科院分区：
文献类型：
--
作者：
Batista, AS;Miletti, LC;Stambuk, BU
蔗糖是酿酒酵母生产面包酵母、燃料乙醇和几种蒸馏饮料的主要碳源。人们普遍认为，蔗糖发酵是通过胞外水解糖进行的，在周质转化酶的介导下，产生葡萄糖和果糖，这些葡萄糖和果糖被输送到细胞内并进行代谢。在目前的工作中，我们分析了酿酒酵母细胞利用蔗糖的一条鲜为人知的途径对蔗糖发酵的贡献，蔗糖通过质膜的主动运输及其细胞内的水解。缺乏主要己糖转运体(hxt1-hxt7和gal2)的酵母菌株不能生长在葡萄糖或果糖上或发酵葡萄糖或果糖。我们的结果表明，由于糖被直接吸收到细胞中，该HXT缺失菌株仍然能够发酵蔗糖。编码高亲和力蔗糖-H+转运蛋白的AGT1基因的缺失使细胞不能进行蔗糖发酵。由于蔗糖不是渗透酶的诱导剂，因此AGT1的表达必须是结构性的，才能使HXT缺失菌株在蔗糖上生长。酿酒酵母细胞活跃的蔗糖运输和发酵的分子特征为优化以甘蔗为基础的工业过程中的酵母开辟了新的机会。版权所有(C)2004 S.Karger AG，巴塞尔。
Sucrose is the major carbon source used by Saccharomyces cerevisiae during production of baker's yeast, fuel ethanol and several distilled beverages. It is generally accepted that sucrose fermentation proceeds through extracellular hydrolysis of the sugar, mediated by the periplasmic invertase, producing glucose and fructose that are transported into the cells and metabolized. In the present work we analyzed the contribution to sucrose fermentation of a poorly characterized pathway of sucrose utilization by S. cerevisiae cells, the active transport of the sugar through the plasma membrane and its intracellular hydrolysis. A yeast strain that lacks the major hexose transporters (hxt1-hxt7 and gal2) is incapable of growing on or fermenting glucose or fructose. Our results show that this hxt-null strain is still able to ferment sucrose due to direct uptake of the sugar into the cells. Deletion of the AGT1 gene, which encodes a high-affi nity sucrose-H+ symporter, rendered cells incapable of sucrose fermentation. Since sucrose is not an inducer of the permease, expression of the AGT1 must be constitutive in order to allow growth of the hxt-null strain on sucrose. The molecular characterization of active sucrose transport and fermentation by S. cerevisiae cells opens new opportunities to optimize yeasts for sugar-cane-based industrial processes. Copyright (C) 2004 S. Karger AG, Basel.