Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France.
FEMS Yeast Res. 2009 Dec;9(8):1172-86. doi: 10.1111/j.1567-1364.2009.00553.x. Epub 2009 Jul 21.
High-level production of bioethanol (140 g L(-1) in 45 h) in aerated fed-batch cultures of Saccharomyces cerevisiae was shown to be linked to the length of a production phase uncoupled to the growth. The induction of this phase was characterized by metabolic and morphologic changes reminiscent of those occurring in the stationary phase of growth on glucose. Global transcriptomic analysis of ethanol-stressed yeast cells in the uncoupling phase harboured features similar to those from stationary-phase cells on glucose. Two distinct cellular populations were isolated by Percoll density-gradient centrifugation in this uncoupling phase. The lower fraction was enriched by yeast cells that were mostly uniform in size and opalescent, containing a large amount of glycogen and trehalose, and exhibiting high respiratory activity. In contrast, the upper fraction was characterized by cells heterogeneous in size, with one to several small buds, which did not contain storage carbohydrates and which exhibited a poor respiratory competence while retaining a high relative glycolytic activity. These results are discussed in terms of a possible induction of a state similar to the quiescence state previously observed from yeast stationary-phase cultures, in response to ethanol toxicity, whose acquisition may be critical for performing high-level alcoholic fermentation.
在有氧补料分批培养的酿酒酵母中，高浓度生产生物乙醇（45 小时内达到 140 g/L）与与生长无关的生产阶段的长度有关。该阶段的诱导表现出与葡萄糖生长静止期相似的代谢和形态变化。对乙醇胁迫下的酵母细胞在解耦阶段的全转录组分析显示出与葡萄糖静止期细胞相似的特征。通过在该解耦阶段用聚蔗糖密度梯度离心分离出两个不同的细胞群体。下部分数富含酵母细胞，这些细胞大小均匀且呈乳光状，含有大量的糖原和海藻糖，表现出高呼吸活性。相比之下，上部分数的特点是细胞大小不均匀，有一个到几个小芽，不含有储存碳水化合物，呼吸能力差，但保持相对较高的糖酵解活性。这些结果与先前在酵母静止期培养物中观察到的可能诱导类似的休眠状态的假设进行了讨论，这是对乙醇毒性的反应，其获得可能对进行高水平酒精发酵至关重要。
