Laboratory of Microbial Genetics, Department of Genetics, Federal University of Pernambuco, Av. Moraes Rego, 1235. Cidade Universitária, Recife, PE, 50.670-901, Brazil.
Department of Antibiotics, Federal University of Pernambuco, Recife, Brazil.
Appl Biochem Biotechnol. 2023 Oct;195(10):6369-6391. doi: 10.1007/s12010-023-04398-w. Epub 2023 Mar 3.
Dekkera bruxellensis has been studied for several aspects of its metabolism over the past years, which has expanded our comprehension on its importance to industrial fermentation processes and uncovered its industrial relevance. Acetate is a metabolite often found in D. bruxellensis aerobic cultivations, whereas its production is linked to decreased ethanol yields. In a previous work, we aimed to understand how acetate metabolism affected the fermentation capacity of D. bruxellensis. In the present work, we evaluated the role of acetate metabolism in respiring cells using ammonium or nitrate as nitrogen sources. Our results showed that galactose is a strictly respiratory sugar and that a relevant part of its carbon is lost, while the remaining is metabolised through the Pdh bypass pathway before being assimilated into biomass. When this pathway was blocked, yeast growth was reduced while more carbon was assimilated to the biomass. In nitrate, more acetate was produced as expected, which increased carbon assimilation, although less galactose was uptaken from the medium. This scenario was not affected by the Pdh bypass inhibition. The confirmation that acetate production was crucial for carbon assimilation was brought by cultivations in pyruvate. All physiological data were connected to the expression patterns of PFK1, PDC1, ADH1, ALD3, ALD5 and ATP1 genes. Other respiring carbon sources could only be properly used by the cells when some external acetate was supplied. Therefore, the results reported herein helped in providing valuable contributions to the understanding of the oxidative metabolism in this potential industrial yeast.
多年来，人们一直在研究德克氏毕赤酵母（Dekkera bruxellensis）在其代谢的多个方面，这扩展了我们对其在工业发酵过程中的重要性的理解，并揭示了其在工业上的相关性。在德克氏毕赤酵母的好氧培养中，通常会发现乙酸盐是一种代谢物，而其产生与乙醇产量的降低有关。在之前的一项研究中，我们旨在了解乙酸盐代谢如何影响德克氏毕赤酵母的发酵能力。在本研究中，我们使用铵盐或硝酸盐作为氮源来评估其在呼吸细胞中的代谢作用。结果表明，半乳糖是一种严格的呼吸性糖，其中一部分碳会丢失，而剩余的碳则通过 Pdh 旁路途径代谢，然后被同化到生物量中。当该途径被阻断时，酵母生长受到抑制，而更多的碳被同化到生物量中。在硝酸盐中，如预期的那样，会产生更多的乙酸盐，从而增加碳的同化，尽管从培养基中摄取的半乳糖减少。这种情况不受 Pdh 旁路抑制的影响。通过丙酮酸培养来确认乙酸盐的产生对碳同化至关重要。所有生理数据都与 PFK1、PDC1、ADH1、ALD3、ALD5 和 ATP1 基因的表达模式相关联。当提供一些外部乙酸盐时，其他呼吸性碳源才能被细胞正确利用。因此，本文的研究结果有助于深入了解这种潜在工业酵母的氧化代谢。
