Department of Food, Environmental and Nutritional Sciences, University of Milan, Via G. Celoria 2, Milan, Italy.
J Ind Microbiol Biotechnol. 2013 Apr;40(3-4):297-303. doi: 10.1007/s10295-012-1229-3. Epub 2013 Jan 25.
Nitrate is one of the most abundant nitrogen sources in nature. Several yeast species have been shown to be able to assimilate nitrate and nitrite, but the metabolic pathway has been studied in very few of them. Dekkera bruxellensis can use nitrate as sole nitrogen source and this metabolic characteristic can render D. bruxellensis able to overcome S. cerevisiae populations in industrial bioethanol fermentations. In order to better characterize how nitrate utilization affects carbon metabolism and the yields of the fermentation products, we investigated this trait in defined media under well-controlled aerobic and anaerobic conditions. Our experiments showed that in D. bruxellensis, utilization of nitrate determines a different pattern of fermentation products. Acetic acid, instead of ethanol, became in fact the main product of glucose metabolism under aerobic conditions. We have also demonstrated that under anaerobic conditions, nitrate assimilation abolishes the "Custers effect", in this way improving its fermentative metabolism. This can offer a new strategy, besides aeration, to sustain growth and ethanol production for the employment of this yeast in industrial processes.
硝酸盐是自然界中最丰富的氮源之一。已经证明几种酵母物种能够同化硝酸盐和亚硝酸盐，但在其中很少有研究其代谢途径。德克氏酵母可以将硝酸盐用作唯一的氮源，这种代谢特性使德克氏酵母能够在工业生物乙醇发酵中克服酿酒酵母种群。为了更好地描述硝酸盐利用如何影响碳代谢和发酵产物的产率，我们在有氧和无氧条件下的定义培养基中研究了这一特性。我们的实验表明，在德克氏酵母中，硝酸盐的利用决定了发酵产物的不同模式。在有氧条件下，实际上乙酸代替了乙醇成为葡萄糖代谢的主要产物。我们还证明，在厌氧条件下，硝酸盐的同化作用消除了“Custers 效应”，从而改善了其发酵代谢。除了通气之外，这为在工业过程中使用这种酵母来维持生长和乙醇生产提供了一种新策略。
