Antonie Van Leeuwenhoek. 2013 Nov;104(5):855-68. doi: 10.1007/s10482-013-9998-x.
The assimilation of nitrate, a nitrogenous compound, was previously described as an important factor favoring Dekkera bruxellensis in the competition with Saccharomyces cerevisiae for the industrial sugarcane substrate. In this substrate, nitrogen sources are limited and diverse, and a recent report showed that amino acids enable D. bruxellensis to grow anaerobically. Thus, understanding the regulation of nitrogen metabolism is one fundamental aspect to comprehend the competiveness of D. bruxellensis in the fermentation environment. In the present study, we evaluated the physiological and transcriptional profiles of D. bruxellensis in response to different carbon and nitrogen supplies to determine their influence on growth, sugar consumption, and ethanol production. Besides, the expression of genes coding for nitrogen permeases and enzymes involved in the biosynthesis of glutamate and energetic metabolism were investigated under these conditions. Our data revealed that genes related to nitrogen uptake in D. bruxellensis are under the control of nitrogen catabolite repression. Moreover, we provide indications that glutamate dehydrogenase and glutamate synthase may switch roles as the major pathway for glutamate biosynthesis in D. bruxellensis. Finally, our data showed that in nonoptimal growth conditions, D. bruxellensis leans toward the respiratory metabolism. The results presented herein show that D. bruxellensis and S. cerevisiae share similar regulation of GDH–GOGAT pathway, while D. bruxellensis converts less glucose to ethanol than S. cerevisiae do when nitrogen is limited. The consequence of this particularity to the industrial process is discussed.
硝酸盐同化作用曾被描述为有利于德克氏酒香酵母（Dekkera bruxellensis）在与酿酒酵母（Saccharomyces cerevisiae）竞争工业甘蔗底物中的一个重要因素。在这种底物中，氮源是有限且多样化的，最近的一份报告表明，氨基酸使 D. bruxellensis 能够在厌氧条件下生长。因此，了解氮代谢的调控是理解 D. bruxellensis 在发酵环境中竞争力的一个基本方面。在本研究中，我们评估了 D. bruxellensis 对不同碳氮供应的生理和转录谱，以确定它们对生长、糖消耗和乙醇生产的影响。此外，还研究了这些条件下编码氮通透酶和参与谷氨酸生物合成和能量代谢的酶的基因表达。我们的数据表明，D. bruxellensis 中的氮摄取相关基因受氮分解代谢物阻遏的控制。此外，我们提供的证据表明，谷氨酸脱氢酶和谷氨酸合酶可能在 D. bruxellensis 中作为谷氨酸生物合成的主要途径转换角色。最后，我们的数据表明，在非最佳生长条件下，D. bruxellensis 倾向于呼吸代谢。本文的研究结果表明，D. bruxellensis 和 S. cerevisiae 共享类似的 GDH-GOGAT 途径调控，而当氮源有限时，D. bruxellensis 将比 S. cerevisiae 更少的葡萄糖转化为乙醇。这一特殊性对工业过程的影响进行了讨论。
