Department of Microbiology, Institute for Biotechnology Applied to Agriculture and Animal Science, Federal University of Viçosa, Viçosa, MG, Brazil.
Antonie Van Leeuwenhoek. 2013 Jan;103(1):153-61. doi: 10.1007/s10482-012-9794-z. Epub 2012 Sep 11.
The fermentation of both glucose and xylose is important to maximize ethanol yield from renewable biomass feedstocks. In this article, we analyze growth, sugar consumption, and ethanol formation by the yeast Kluyveromyces marxianus UFV-3 using various glucose and xylose concentrations and also under conditions of reduced respiratory activity. In almost all the conditions analyzed, glucose repressed xylose assimilation and xylose consumption began after glucose had been exhausted. A remarkable difference was observed when mixtures of 5 g L(-1) glucose/20 g L(-1) xylose and 20 g L(-1) glucose/20 g L(-1) xylose were used. In the former, the xylose consumption began immediately after the glucose depletion. Indeed, there was no striking diauxic phase, as observed in the latter condition, in which there was an interval of 30 h between glucose depletion and the beginning of xylose consumption. Ethanol production was always higher in a mixture of glucose and xylose than in glucose alone. The highest ethanol concentration (8.65 g L(-1)) and cell mass concentration (4.42 g L(-1)) were achieved after 8 and 74 h, respectively, in a mixture of 20 g L(-1) glucose/20 g L(-1) xylose. When inhibitors of respiration were added to the medium, glucose repression of xylose consumption was alleviated completely and K. marxianus was able to consume xylose and glucose simultaneously.
利用不同浓度的葡萄糖和木糖，并在呼吸活性降低的条件下，分析了马克斯克鲁维酵母 UFV-3 的生长、糖消耗和乙醇形成情况。在分析的几乎所有条件下，葡萄糖都抑制了木糖的同化，并且在葡萄糖耗尽后才开始消耗木糖。当使用 5 g/L 葡萄糖/20 g/L 木糖和 20 g/L 葡萄糖/20 g/L 木糖的混合物时，观察到了显著的差异。在前一种情况下，葡萄糖耗尽后立即开始消耗木糖。实际上，与后一种情况不同，没有明显的双相发酵阶段，在后一种情况下，葡萄糖耗尽和木糖消耗开始之间有 30 h 的间隔。在葡萄糖和木糖的混合物中，乙醇的产量总是高于单独使用葡萄糖时。在 20 g/L 葡萄糖/20 g/L 木糖的混合物中，分别在 8 和 74 h 后达到了最高乙醇浓度（8.65 g/L）和细胞质量浓度（4.42 g/L）。当向培养基中添加呼吸抑制剂时，葡萄糖对木糖消耗的抑制作用完全缓解，马克斯克鲁维酵母能够同时消耗木糖和葡萄糖。
