| 1. |
|
|
| 2. |
- Dashko, Sofia, et al.
(author)
-
Why, when and how did yeast evolve alcoholic fermentation?
- 2014
-
In: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 14:6, s. 826-832
-
Research review (peer-reviewed)abstract
- The origin of modern fruits brought to microbial communities an abundant source of rich food based on simple sugars. Yeasts, especially Saccharomyces cerevisiae, usually become the predominant group in these niches. One of the most prominent and unique features and likely a winning trait of these yeasts is their ability to rapidly convert sugars to ethanol at both anaerobic and aerobic conditions. Why, when and how did yeast remodel their carbon metabolism to be able to accumulate ethanol under aerobic conditions and at the expense of decreasing biomass production? We hereby review the recent data on the carbon metabolism in Saccharomycetaceae species, and attempt to reconstruct the ancient environment, which could promote the evolution of alcoholic fermentation. We speculate that the first step towards the so-called alcoholic fermentation lifestyle was the exploration of anaerobic niches resulting in an increased metabolic capacity to degrade sugar to ethanol. The strengthened glycolytic flow had in parallel a beneficial effect on the microbial competition outcome, and later evolved as a "new" tool promoting the yeast competition ability under aerobic conditions. The basic aerobic alcoholic fermentation ability was subsequently "upgraded" in several lineages by evolving additional regulatory steps, like glucose repression in the S. cerevisiae clade, to achieve a more precise metabolic control. This article is protected by copyright. All rights reserved.
|
|
| 3. |
- Galafassi, Silvia, et al.
(author)
-
Dekkera/Brettanomyces yeasts for ethanol production from renewable sources under oxygen-limited and low-pH conditions
- 2011
-
In: Journal of Industrial Microbiology & Biotechnology. - : Oxford University Press (OUP). - 1367-5435 .- 1476-5535. ; 38:8, s. 1079-1088
-
Journal article (peer-reviewed)abstract
- Industrial fermentation of lignocellulosic hydrolysates to ethanol requires microorganisms able to utilise a broad range of carbon sources and generate ethanol at high yield and productivity. D. bruxellensis has recently been reported to contaminate commercial ethanol processes, where it competes with Saccharomyces cerevisiae [4, 26]. In this work Brettanomyces/Dekkera yeasts were studied to explore their potential to produce ethanol from renewable sources under conditions suitable for industrial processes, such as oxygen-limited and low-pH conditions. Over 50 strains were analysed for their ability to utilise a variety of carbon sources, and some strains grew on cellobiose and pentoses. Two strains of D. bruxellensis were able to produce ethanol at high yield (0.44 g g(-1) glucose), comparable to those reported for S. cerevisiae. B. naardenensis was shown to be able to produce ethanol from xylose. To obtain ethanol from synthetic lignocellulosic hydrolysates we developed a two-step fermentation strategy: the first step under aerobic conditions for fast production of biomass from mixtures of hexoses and pentoses, followed by a second step under oxygen limitation to promote ethanol production. Under these conditions we obtained biomass and ethanol production on synthetic lignocellulosic hydrolysates, with ethanol yields ranging from 0.2 to 0.3 g g(-1) sugar. Hexoses, xylose and arabinose were consumed at the end of the process, resulting in 13 g l(-1) of ethanol, even in the presence of furfural. Our studies showed that Brettanomyces/Dekkera yeasts have clear potential for further development for industrial processes aimed at production of ethanol from renewable sources.
|
|
| 4. |
- Galafassi, Silvia, et al.
(author)
-
Osmotic stress response in the wine yeast Dekkera bruxellensis
- 2013
-
In: Food Microbiology. - : Elsevier BV. - 1095-9998 .- 0740-0020. ; 36:2, s. 316-319
-
Journal article (peer-reviewed)abstract
- Dekkera bruxellensis is mainly associated with Iambic beer fermentation and wine production and may contribute in a positive or negative manner to the flavor development. This yeast is able to produce phenolic compounds, such as 4-ethylguaiacol and 4-ethylphenol which could spoil the wine, depending on their concentration. In this work we have investigated how this yeast responds when exposed to conditions causing osmotic stress, as high sorbitol or salt concentrations. We observed that osmotic stress determined the production and accumulation of intracellular glycerol, and the expression of NADH-dependent glycerol-3-phosphate dehydrogenase (GPO) activity was elevated. The involvement of the HOG MAPK pathway in response to this stress condition was also investigated. We show that in D. bruxellensis Hog1 protein is activated by phosphorylation under hyperosmotic conditions, highlighting the conserved role of HOG MAP kinase signaling pathway in the osmotic stress response. Gene Accession numbers in GenBank: DbHOG1: JX65361, DbSTL1: JX965362. (C) 2013 Elsevier Ltd. All rights reserved.
|
|
| 5. |
- Hagman, Arne, et al.
(author)
-
Yeast "make-accumulate-consume" life strategy evolved as a multi-step process that predates the whole genome duplication.
- 2013
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7
-
Journal article (peer-reviewed)abstract
- When fruits ripen, microbial communities start a fierce competition for the freely available fruit sugars. Three yeast lineages, including baker's yeast Saccharomyces cerevisiae, have independently developed the metabolic activity to convert simple sugars into ethanol even under fully aerobic conditions. This fermentation capacity, named Crabtree effect, reduces the cell-biomass production but provides in nature a tool to out-compete other microorganisms. Here, we analyzed over forty Saccharomycetaceae yeasts, covering over 200 million years of the evolutionary history, for their carbon metabolism. The experiments were done under strictly controlled and uniform conditions, which has not been done before. We show that the origin of Crabtree effect in Saccharomycetaceae predates the whole genome duplication and became a settled metabolic trait after the split of the S. cerevisiae and Kluyveromyces lineages, and coincided with the origin of modern fruit bearing plants. Our results suggest that ethanol fermentation evolved progressively, involving several successive molecular events that have gradually remodeled the yeast carbon metabolism. While some of the final evolutionary events, like gene duplications of glucose transporters and glycolytic enzymes, have been deduced, the earliest molecular events initiating Crabtree effect are still to be determined.
|
|
| 6. |
- Merico, Annamaria, et al.
(author)
-
Fermentative lifestyle in yeasts belonging to the Saccharomyces complex
- 2007
-
In: The FEBS Journal. - : Wiley. - 1742-464X. ; 274:4, s. 976-989
-
Journal article (peer-reviewed)abstract
- The yeast Saccharomyces cerevisiae is characterized by its ability to: (a) degrade glucose or fructose to ethanol, even in the presence of oxygen (Crabtree effect); (b) grow in the absence of oxygen; and (c) generate respiratory-deficient mitochondrial mutants, so-called petites. How unique are these properties among yeasts in the Saccharomyces clade, and what is their origin? Recent progress in genome sequencing has elucidated the phylogenetic relationships among yeasts in the Saccharomyces complex, providing a framework for the understanding of the evolutionary history of several modern traits. In this study, we analyzed over 40 yeasts that reflect over 150 million years of evolutionary history for their ability to ferment, grow in the absence of oxygen, and generate petites. A great majority of isolates exhibited good fermentation ability, suggesting that this trait could already be an intrinsic property of the progenitor yeast. We found that lineages that underwent the whole-genome duplication, in general, exhibit a fermentative lifestyle, the Crabtree effect, and the ability to grow without oxygen, and can generate stable petite mutants. Some of the pre-genome duplication lineages also exhibit some of these traits, but a majority of the tested species are petite-negative, and show a reduced Crabtree effect and a reduced ability to grow in the absence of oxygen. It could be that the ability to accumulate ethanol in the presence of oxygen, a gradual independence from oxygen and/or the ability to generate petites were developed later in several lineages. However, these traits have been combined and developed to perfection only in the lineage that underwent the whole-genome duplication and led to the modern Saccharomyces cerevisiae yeast.
|
|
| 7. |
- Merico, Annamaria, et al.
(author)
-
The oxygen level determines the fermentation pattern in Kluyveromyces lactis
- 2009
-
In: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 9:5, s. 749-756
-
Journal article (peer-reviewed)abstract
- Yeasts belonging to the lineage that underwent whole-genome duplication (WGD) possess a good fermentative potential and can proliferate in the absence of oxygen. In this study, we analyzed the pre-WGD yeast Kluyveromyces lactis and its ability to grow under oxygen-limited conditions. Under these conditions, K. lactis starts to increase the glucose metabolism and accumulates ethanol and glycerol. However, under more limited conditions, the fermentative metabolism decreases, causing a slow growth rate. In contrast, Saccharomyces cerevisiae and Saccharomyces kluyveri in anaerobiosis exhibit almost the same growth rate as in aerobiosis. In this work, we showed that in K. lactis, under oxygen-limited conditions, a decreased expression of RAG1 occurred. The activity of glucose-6-phosphate dehydrogenase also decreased, likely causing a reduced flux in the pentose phosphate pathway. Comparison of related and characterized yeasts suggests that the behavior observed in K. lactis could reflect the lack of an efficient mechanism to maintain a high glycolytic flux and to balance the redox homeostasis under hypoxic conditions. This could be a consequence of a recent specialization of K. lactis toward living in a niche where the ethanol accumulation at high oxygen concentrations and the ability to survive at a low oxygen concentration do not represent an advantage.
|
|
| 8. |
- Moktaduzzaman, Md, et al.
(author)
-
Galactose utilization sheds new light on sugar metabolism in the sequenced strain Dekkera bruxellensis CBS 2499.
- 2015
-
In: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 15:2, s. 009-9
-
Journal article (peer-reviewed)abstract
- Dekkera bruxellensis and Saccharomyces cerevisiae are considered two phylogenetically distant relatives, but they share several industrial relevant traits such as the ability to produce ethanol under aerobic conditions (Crabtree effect), high tolerance towards ethanol and acids, and ability to grow without oxygen. Beside a huge adaptability, D. bruxellensis exhibits a broader spectrum in utilization of carbon and nitrogen sources in comparison to S. cerevisiae. With the aim to better characterize its carbon source metabolism and regulation, the usage of galactose and the role that glucose plays on sugar metabolism were investigated in D. bruxellensis CBS 2499. The results indicate that in this yeast galactose is a non-fermentable carbon source, in contrast to S. cerevisiae that can ferment it. In particular, its metabolism is affected by the nitrogen source. Interestingly, D. bruxellensis CBS 2499 exhibits the 'short-term Crabtree effect', and the expression of genes involved in galactose utilization and in respiratory metabolism is repressed by glucose, similarly to what occurs in S. cerevisiae.
|
|
| 9. |
- Piskur, Jure, et al.
(author)
-
The genome of wine yeast Dekkera bruxellensis provides a tool to explore its food-related properties.
- 2012
-
In: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605. ; 157:2, s. 202-209
-
Journal article (peer-reviewed)abstract
- The yeast Dekkera/Brettanomyces bruxellensis can cause enormous economic losses in wine industry due to production of phenolic off-flavor compounds. D. bruxellensis is a distant relative of baker's yeast Saccharomyces cerevisiae. Nevertheless, these two yeasts are often found in the same habitats and share several food-related traits, such as production of high ethanol levels and ability to grow without oxygen. In some food products, like lambic beer, D. bruxellensis can importantly contribute to flavor development. We determined the 13.4Mb genome sequence of the D. bruxellensis strain Y879 (CBS2499) and deduced the genetic background of several "food-relevant" properties and evolutionary history of this yeast. Surprisingly, we find that this yeast is phylogenetically distant to other food-related yeasts and most related to Pichia (Komagataella) pastoris, which is an aerobic poor ethanol producer. We further show that the D. bruxellensis genome does not contain an excess of lineage specific duplicated genes nor a horizontally transferred URA1 gene, two crucial events that promoted the evolution of the food relevant traits in the S. cerevisiae lineage. However, D. bruxellensis has several independently duplicated ADH and ADH-like genes, which are likely responsible for metabolism of alcohols, including ethanol, and also a range of aromatic compounds.
|
|
| 10. |
- Rozpedowska, Elzbieta, et al.
(author)
-
Candida albicans- a pre-whole genome duplication yeast is predominantly aerobic and a poor ethanol producer.
- 2011
-
In: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 11:3, s. 285-291
-
Journal article (peer-reviewed)abstract
- Yeast species belonging to the lineage that underwent the whole genome duplication (WGD), and including Saccharomyces cerevisiae, can grow under anaerobiosis and accumulate ethanol in the presence of glucose and oxygen. The pre-WGD yeasts, which branched from the S. cerevisiae lineage just prior to the WGD event, including Kluyveromyces lactis, are more dependent on oxygen and do not accumulate large amounts of ethanol in the presence of excess oxygen. Yeasts that belong to the so-called 'lower branches' of the yeast phylogenetic tree and diverged from S. cerevisiae more than 200 million years ago, have so far not been thoroughly investigated for their physiology and carbon metabolism. We have hereby studied several isolates of Candida albicans and Debaryomyces hansenii for their dependence on oxygen. C. albicans grew very poorly at oxygen concentration below 1 p.p.m. and D. hansenii could not grow at all. In aerobic batch cultivations C. albicans exhibited a predominately aerobic metabolism, accumulating only small amounts of ethanol (0.01-0.09 g g(-1) glucose). Apparently, C. albicans and several other pre-WGD yeasts still exhibit the original traits of the yeast progenitor: poor accumulation of ethanol under aerobic conditions and strong dependence on the presence of oxygen.
|
|
