| 1. |
- Mukherjee, Vaskar, 1986, et al.
(författare)
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Polygenic analysis of high osmotolerance in Saccharomyces cerevisiae
- 2015
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Ingår i: Abstracts of the 27th International Conference on Yeast Genetics and Molecular Biology. - : Wiley. ; 32:S1
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of our research is to investigate the molecular basis of superior osmotolerance in Saccharomyces cerevisiae and to identify unique mutations in the causative genes that are responsible for superior fermentation performance under very high gravity fermentation. We employed pooled-segregant whole-genome sequence analysis, a technology for efficient polygenic analysis of complex traits developed in our laboratory. For that purpose, a haploid segregant of an osmotolerant yeast strain with the best superior phenotype has been crossed with a haploid segregant from an unrelated industrial strain with a comparatively inferior phenotype. The diploid hybrid has been sporulated and about 30 segregants with the superior phenotype have been selected to construct the superior pool. About 30 segregants were also randomly selected regardless of their phenotype to construct the unselected pool. Pooled genomic DNA extraction was performed for both pools separately and submitted to custom whole-genome sequence analysis. The two parent strains have also been sent for sequencing to determine all SNPs. The variant frequency of the SNPs in the pool has been used to map the QTLs containing the causative mutations in the genome. Several clear QTLs with different strength have been identified in this way. This is followed by the application of reciprocal hemizygosity analysis to identify the causative gene(s) with the responsible mutation in the mapped loci. Finally the identified causative mutations will be introduced in to industrial strains to improve the very high gravity bioethanol fermentation performance.
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| 2. |
- Radecka, Dorota, et al.
(författare)
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Looking beyond Saccharomyces: the potential of non-conventional yeast species for desirable traits in bioethanol fermentation
- 2015
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 15:6
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Forskningsöversikt (refereegranskat)abstract
- Saccharomyces cerevisiae has been used for millennia in the production of food and beverages and is by far the most studied yeast species. Currently, it is also the most used microorganism in the production of first-generation bioethanol from sugar or starch crops. Second-generation bioethanol, on the other hand, is produced from lignocellulosic feedstocks that are pretreated and hydrolyzed to obtain monomeric sugars, mainly D-glucose, D-xylose and L-arabinose. Recently, S. cerevisiaerecombinant strains capable of fermenting pentose sugars have been generated. However, the pretreatment of the biomass results in hydrolysates with high osmolarity and high concentrations of inhibitors. These compounds negatively influence the fermentation process. Therefore, robust strains with high stress tolerance are required. Up to now, more than 2000 yeast species have been described and some of these could provide a solution to these limitations because of their high tolerance to the most predominant stress conditions present in a second-generation bioethanol reactor. In this review, we will summarize what is known about the non-conventional yeast species showing unusual tolerance to these stresses, namely Zygosaccharomyces rouxii(osmotolerance), Kluyveromyces marxianus and Ogataea (Hansenula) polymorpha(thermotolerance), Dekkera bruxellensis (ethanol tolerance), Pichia kudriavzevii (furan derivatives tolerance) and Z. bailii (acetic acid tolerance).
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| 3. |
- Ruyters, Stefan, et al.
(författare)
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Assessing the potential of wild yeasts for bioethanol production
- 2015
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Ingår i: Journal of Industrial Microbiology and Biotechnology. - : Oxford University Press (OUP). - 1367-5435 .- 1476-5535. ; 42:1, s. 39-48
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Tidskriftsartikel (refereegranskat)abstract
- Bioethanol fermentations expose yeasts to a new, complex and challenging fermentation medium with specific inhibitors and sugar mixtures depending on the type of carbon source. It is, therefore, suggested that the natural diversity of yeasts should be further exploited in order to find yeasts with good ethanol yield in stressed fermentation media. In this study, we screened more than 50 yeast isolates of which we selected five isolates with promising features. The species Candida bombi, Wickerhamomyces anomalus and Torulaspora delbrueckii showed better osmo- and hydroxymethylfurfural tolerance than Saccharomyces cerevisiae. However, S. cerevisiae isolates had the highest ethanol yield in fermentation experiments mimicking high gravity fermentations (25 % glucose) and artificial lignocellulose hydrolysates (with a myriad of inhibitors). Interestingly, among two tested S. cerevisiaestrains, a wild strain isolated from an oak tree performed better than Ethanol Red, a S. cerevisiae strain which is currently commonly used in industrial bioethanol fermentations. Additionally, a W. anomalus strain isolated from sugar beet thick juice was found to have a comparable ethanol yield, but needed longer fermentation time. Other non-Saccharomycesyeasts yielded lower ethanol amounts.
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