| 1. |
- Ishchuk, Olena P., et al.
(författare)
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Novel centromeric loci of the wine and beer yeast dekkera bruxellensis CEN1 and CEN2
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- The wine and beer yeast Dekkera bruxellensis thrives in environments that are harsh and limiting, especially in concentrations with low oxygen and high ethanol. Its different strains' chromosomes greatly vary in number (karyotype). This study isolates two novel centromeric loci (CEN1 and CEN2), which support both the yeast's autonomous replication and the stable maintenance of plasmids. In the sequenced genome of the D. bruxellensis strain CBS 2499, CEN1 and CEN2 are each present in one copy. They differ from the known "point" CEN elements, and their biological activity is retained within ~900-1300 bp DNA segments. CEN1 and CEN2 have features of both "point" and "regional" centromeres: They contain conserved DNA elements, ARSs, short repeats, one tRNA gene, and transposon-like elements within less than 1 kb. Our discovery of a miniature inverted-repeat transposable element (MITE) next to CEN2 is the first report of such transposons in yeast. The transformants carrying circular plasmids with cloned CEN1 and CEN2 undergo a phenotypic switch: They form fluffy colonies and produce three times more biofilm. The introduction of extra copies of CEN1 and CEN2 promotes both genome rearrangements and ploidy shifts, with these effects mediated by homologous recombination (between circular plasmid and genome centromere copy) or by chromosome breakage when integrated. Also, the proximity of the MITE-like transposon to CEN2 could translocate CEN2 within the genome or cause chromosomal breaks, so promoting genome dynamics. With extra copies of CEN1 and CEN2, the yeast's enhanced capacities to rearrange its genome and to change its gene expression could increase its abilities for exploiting new and demanding niches.
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| 2. |
- Schifferdecker, Anna, et al.
(författare)
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Alcohol dehydrogenase gene ADH3 activates glucose alcoholic fermentation in genetically engineered Dekkera bruxellensis yeast.
- 2016
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598.
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Tidskriftsartikel (refereegranskat)abstract
- Dekkera bruxellensis is a non-conventional Crabtree-positive yeast with a good ethanol production capability. Compared to Saccharomyces cerevisiae, its tolerance to acidic pH and its utilization of alternative carbon sources make it a promising organism for producing biofuel. In this study, we developed an auxotrophic transformation system and an expression vector, which enabled the manipulation of D. bruxellensis, thereby improving its fermentative performance. Its gene ADH3, coding for alcohol dehydrogenase, was cloned and overexpressed under the control of the strong and constitutive promoter TEF1. Our recombinant D. bruxellensis strain displayed 1.4 and 1.7 times faster specific glucose consumption rate during aerobic and anaerobic glucose fermentations, respectively; it yielded 1.2 times and 1.5 times more ethanol than did the parental strain under aerobic and anaerobic conditions, respectively. The overexpression of ADH3 in D. bruxellensis also reduced the inhibition of fermentation by anaerobiosis, the "Custer effect". Thus, the fermentative capacity of D. bruxellensis could be further improved by metabolic engineering.
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| 3. |
- Schifferdecker, Anna
(författare)
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Development of molecular biology tools for the wine and beer yeast Dekkera bruxellensis
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The non-conventional wine and beer yeast Dekkera bruxellensis is of great interest for the food industry and academic research. This Crabtree-positive yeast is a good ethanol producer and can compete the baker´s yeast Saccharomyces cerevisiae, in ethanol and pH tolerance and could be an even better organism for the biofuel production from alternative carbon sources. D. bruxellensis is considered to be one of the main spoilage organisms in the wine and biofuel industry; on the other hand, it is ‘indispensable’ as a contributor to the flavor profile of Belgium lambic and gueuze beers. It also adds characteristic aromatic properties to some red wines and sourdough. There are not many molecular tools available for this yeast species. During my PhD project I characterized some D. bruxellensis promoters and analyzed their expression activity in response to different carbon sources. This led me to the construction of a D. bruxellensis expression vector. Furthermore I analyzed the role of alcohol dehydrogenase gene isoform III (ADH3) in the glucose fermentation and ethanol production. I have also analyzed a collection of 170 strains of the Dekkera/ Brettanomyces genus isolated from different niches from different parts of the world. These strains have been phenotypically characterized regarding the traits as ethanol, pH and temperature resistance, utilization of different carbon and nitrogen sources and osmotolerance. Some of the strains were studied with further genetic analyses. This gives us a better knowledge of the relationship of the phenotype and the genotype in this genus. Non-conventional yeasts represent a vast potential for industrial application, but most of them have not been characterized yet. I have analyzed 14 non-conventional yeasts for their ability to be alternatives to baker´s yeast. Seven of these strains have been used for baking bread. Two strains (Kazachstania gamospora, Wickerhamomyces subpelliculosus) exhibited the same or even better leavening abilities (production of carbon dioxide, resistance towards high sodium chloride and sugar concentrations) comparing to commercial baker´s yeast. On the other hand, the selected strains exhibited an extraordinary taste. This could be further used in the industry for the production of bread with new flavours. In conclusion, the research presented in this thesis broadens the knowledge about Dekkera/ Brettanomyces yeasts (particularly D. bruxellensis) by delivering molecular tools to manipulate this species. These tools are necessary to further identify and characterize genes of interest. Additionally, the identification of two alternative baker´s yeasts picked out of the huge bulk of non-conventional yeasts illustrates how fruitful research into yet uncharacterized species can be to discover their useful qualities and abilities.
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| 4. |
- Schifferdecker, Anna, et al.
(författare)
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The wine and beer yeast Dekkera bruxellensis.
- 2014
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Ingår i: Yeast. - : Wiley. - 1097-0061 .- 0749-503X. ; 31:9, s. 323-332
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the non-conventional yeast Dekkera bruxellensis has been gaining more and more attention in the food industry and academic research. This yeast species is a distant relative of Saccharomyces cerevisiae, and especially known for two important characteristics: on one hand it is considered to be one of the main spoilage organisms in the wine and bioethanol industry, on the other hand it is "indispensable" as a contributor to the flavour profile of Belgium lambic and gueuze beers. Additionally, it adds to the characteristic aromatic properties of some red wines. Recently this yeast has also become a model to study yeast evolution. In this review we focus on the recently developed molecular and genetic tools, such as complete genome sequencing and transformation, to study and manipulate this yeast. We also focus on the areas which are particularly well explored in this yeast, such as the synthesis of off-flavours, yeast detection methods, carbon metabolism and evolutionary history. This article is protected by copyright. All rights reserved.
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| 5. |
- Zhou, Nerve, et al.
(författare)
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Kazachstania gamospora and Wickerhamomyces subpelliculosus : Two alternative baker's yeasts in the modern bakery
- 2017
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605. ; 250, s. 45-58
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Tidskriftsartikel (refereegranskat)abstract
- Saccharomyces cerevisiae, the conventional baker's yeast, remains the most domesticated yeast monopolizing the baking industry. Its rapid consumption of sugars and production of CO2 are the most important attributes required to leaven the dough. New research attempts highlight that these attributes are not unique to S. cerevisiae, but also found in several non-conventional yeast species. A small number of these yeast species with similar properties have been described, but remain poorly studied. They present a vast untapped potential for the use as leavening agents and flavor producers due to their genetic and phylogenetic diversity. We assessed the potential of several non-conventional yeasts as leavening agents and flavor producers in dough-like conditions in the presence of high sugar concentrations and stressful environments mimicking conditions found in flour dough. We tested the capabilities of bread leavening and aroma formation in a microbread platform as well as in a bakery setup. Bread leavened with Kazachstania gamospora and Wickerhamomyces subpelliculosus had better overall results compared to control baker's yeast. In addition, both displayed higher stress tolerance and broader aroma profiles than the control baker's yeast. These attributes are important in bread and other farinaceous products, making K. gamospora and W. subpelliculosus highly applicable as alternative baker's yeasts.
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