217 research outputs found
Elucidating flavour formation and stress tolerance in brewing yeast hybrids
No full textLager beer is one of the most popular beverages worldwide, and lager yeast, a natural interspecific hybrid between Saccharomyces cerevisiae and Saccharomyces eubayanus, is one of the most important industrial microorganisms. Its success is likely due to a combination of traits not commonly found in pure yeast species: low-temperature tolerance from S. eubayanus, and maltotriose utilization from S. cerevisiae. However, the diversity of lager yeast in industrial use is currently limited.
In an attempt to increase the genetic and phenotypic diversity of lager yeast, we explored the possibility of using interspecific hybridization as a non-GM method to produce de novo hybrids with tailored properties, by mating selected strains of S. cerevisiae and S. eubayanus. In addition to establishing strain development methodology, we aimed to elucidate mechanisms responsible for phenotypes observed in the newly created strains.
The new hybrids had not only inherited beneficial properties from both parent strains, but in many cases also showed apparent hybrid vigour, fermenting faster and producing beer with higher concentrations of alcohol and flavour-active esters than the parents. Interspecific hybridization can therefore be applied not only for production of novel non-GM lager yeast strains, but also to improve brewing-relevant traits relative to parent strains.
In addition, we developed methodology that allowed creation of hybrids with multiple parent strains and removal of undesirable phenolic off-flavour through the use of fertile allotetraploid intermediates. We also showed that the inherent genomic instability of hybrids could be exploited to generate variant strains by adaptive evolution. Adapted variants outperformed non-adapted strains during wort fermentation, and the majority also possessed several desirable brewing-relevant traits.
Ploidy levels of the generated hybrids influenced fermentation properties, as higher ploidy hybrids fermented faster and produced higher concentrations of flavour-active esters. Higher gene copy numbers and expression levels were observed for relevant genes. We also observed significant variation in lipid composition of parent and hybrid strains at different fermentation temperatures and ethanol contents. Strains which performed well at low temperatures and/or high ethanol concentrations were associated with increased concentrations of lipids containing unsaturated fatty acids.
Results demonstrated the potential of interspecific hybridization as a valuable tool for developing new lager yeast strains, and may also help to elucidate the evolutionary history of industrial lager yeast strains.
Hybridization of saccharomyces cerevisiae sourdough strains with cryotolerant saccharomyces bayanus nbrc1948 as a strategy to increase diversity of strains available for lager beer fermentation
Get PDFThe search for novel brewing strains from non-brewing environments represents an emerging trend to increase genetic and phenotypic diversities in brewing yeast culture collections. Another valuable tool is hybridization, where beneficial traits of individual strains are combined in a single organism. This has been used successfully to create de novo hybrids from parental brewing strains by mimicking natural Saccharomyces cerevisiae ale × Saccharomyces eubayanus lager yeast hybrids. Here, we integrated both these approaches to create synthetic hybrids for lager fermentation using parental strains from niches other than beer. Using a phenotype-centered strategy, S. cerevisiae sourdough strains and the S. eubayanus × Saccharomyces uvarum strain NBRC1948 (also referred to as Saccharomyces bayanus) were chosen for their brewing aptitudes. We demonstrated that, in contrast to S. cerevisiae × S. uvarum crosses, hybridization yield was positively affected by time of exposure to starvation, but not by staggered mating. In laboratory-scale fermentation trials at 20◦ C, one triple S. cerevisiae × S. eubayanus × S. uvarum hybrid showed a heterotic phenotype compared with the parents. In 2 L wort fermentation trials at 12◦ C, this hybrid inherited the ability to consume efficiently maltotriose from NBRC1948 and, like the sourdough S. cerevisiae parent, produced appreciable levels of the positive aroma compounds 3-methylbutyl acetate (banana/pear), ethyl acetate (general fruit aroma) and ethyl hexanoate (green apple, aniseed, and cherry aroma). Based on these evidences, the phenotype-centered approach appears promising for designing de novo lager beer hybrids and may help to diversify aroma profiles in lager beer
Bioprospecting for brewers: Exploiting natural diversity for naturally diverse beers
No full textThe burgeoning interest in archaic, traditional, and novel beer styles has coincided with a growing appreciation of the role of yeasts in determining beer character as well as a better understanding of the ecology and biogeography of yeasts. Multiple studies in recent years have highlighted the potential of wild Saccharomyces and non‐Saccharomyces yeasts for production of beers with novel flavour profiles and other desirable properties. Yeasts isolated from spontaneously fermented beers as well as from other food systems (wine, bread, and kombucha) have shown promise for brewing application, and there is evidence that such cross‐system transfers have occurred naturally in the past. We review here the available literature pertaining to the use of nonconventional yeasts in brewing, with a focus on the origins of these yeasts, including methods of isolation. Practical aspects of utilizing nondomesticated yeasts are discussed, and modern methods to facilitate discovery of yeasts with brewing potential are highlighted.N. Grijalva Vallejos acknowledges the “Secretaría de Educación Superior, Ciencia, Tecnología e Innovación” (SENESCYT) of Ecuador, for the predoctoral grant awarded. The Academy of Finland (Academy Projects 276480 and 305453) is gratefully acknowledged for supporting the work of B. Gibson. J. Nikulin is supported by Fonds Baillet Latour. K. Krogerus wishes to thank the Alfred Kordelin Foundation, Svenska Kulturfonden—The Swedish Cultural Foundation in Finland, and Suomen Kulttuurirahasto for their support.Peer reviewe
Development of a new brewing strain with improved aroma through hybridization and UV mutagenesis
No full textYeasts are fundamental in beer production, influencing fermentation, flavor, and stability. To meet consumer demand, we developed a novel, GMO-free yeast hybrid between a sourdough strain of Saccharomyces cerevisiae and a cryotolerant S. eubayanus x S. bayanus via spore-to-spore hybridization. Microfermentations showed improved brewing traits in one hybrid but also the undesired Phenolic Off-Flavor (POF+) phenotype, caused by the conversion of ferulic acid into 4-vinyl guaiacol (4VG). To eliminate this trait, we applied UV mutagenesis, optimizing irradiation conditions (50 cm distance, 30 s exposure) to achieve 8-22% mortality. Nystatin treatment, which selects slow-growing mutants, reduced the mutation success rate (13.3% without vs. 0.4% with nystatin). Mutants were screened on YPDA with 4 mM ferulic acid and analyzed via Ferulic Acid Conversion Index (FACI) and Cinnamic Acid Sensitivity Index (CASI). POF- candidates exhibited low FACI and high CASI values, confirming reduced 4VG production. Further microfermentations confirmed that selected mutants retained improved brewing traits without the POF+ phenotype. This study demonstrates that hybridization combined with UV mutagenesis is an effective, GMO-free strategy for developing superior brewing yeasts
Genome assemblies related to preprint "European Farmhouse Brewing Yeasts Form a Distinct Genetic Group"
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Inverkan av vörtens valinhalt på mängden diacetyl som produceras under jäsningen av öl
Get PDFDiacetyl and 2,3-pentanedione are butter-tasting vicinal diketones produced as by-products of valine and isoleucine biosynthesis during wort fermentation, and their presence in beer is usually unwanted.
Yeast are able to reduce diacetyl and 2,3-pentanedione into compounds with higher flavour thresholds, and this is usually achieved during a resource-and time-consuming maturation phase after the primary fermentation.
One promising method of decreasing diacetyl production during fermentation is through the control of the valine content of the wort, since valine is involved with the feedback inhibition of enzymes controlling the valine biosynthesis pathway and indirectly the formation of diacetyl precursors.
The objective of this thesis was to investigate the influence of valine supplementation, wort amino acid profile and free amino nitrogen content on diacetyl formation during wort fermentation with the lager yeast Saccharomyces pastorianus, by carrying out a series of small-scale (2-litre) and medium-scale (10-litre) fermentations, which were sampled and analysed for diacetyl and amino acid concentrations, along with standard beer parameters.
Supplementation of valine to the wort resulted in decreased maximum (up to 37% lower) and final (up to 33% lower) diacetyl concentrations in all trials, and the composition of the amino acid spectrum of the wort also had an impact on diacetyl and 2,3-pentanedione production during fermentation.
The results suggest that there is no correlation between the concentrations of wort amino acids and diacetyl production per se, but rather a negative correlation between the uptake rate of valine (and also other branched-chain amino acids) and diacetyl production was found.
The results from all four experiments agree that fermentation performance and yeast growth was not affected by the studied levels of amino acid supplementations, implying that supplementation of valine or other amino acids will not affect the fermentation time nor the attenuation level achieved.
Supplementation of amino acids did however have a minor effect on the concentrations of higher alcohols and esters linked to the amino acids via the Ehrlich pathway, suggesting that large levels of supplementation could affect the flavour profile of the beer.
It can be concluded that modifying the amino acid profile of wort, especially in respect to valine and the other branched-chain amino acids, is an effective way of decreasing the amount of diacetyl formed during fermentation.
This knowledge can be utilized for decreasing the maturation time of beer, however further research is required before it becomes feasible at an industrial scale
Nyutveckling av Huddigs spakkonsoler för modellerna 1060 och 1260
No full textSammanfattning Författaren Kristoffer Larsson har skrivit rapporten tillsammans med grävlastarstillverkaren Huddig i Hudiksvall. Rapporten beskriver nyutvecklingen av Huddigs spakkonsoler. Bakgrunden till examensarbetet är att Huddig har haft kontinuerlig utveckling av sin interiör och hytt men spakkonsolerna har inte följt med i den utvecklingen. Målet med examensarbetet var att ta fram fyra olika prototyper med hänsyn på utformning, handergonomi, knapplacering, trängstyrningsfunktion, rototilt, materialval och tillverkningsmetod. För att författaren skulle få en bild av vad det fanns för kundsynpunkter och vad andra personen som har en relation till Huddig har för synpunkter gjordes en marknadsundersökning. Därefter följde arbetet med att bryta ned arbetet och produkten i delar med olika metoder. Åtta olika konceptförslag skissades fram och slutligen sållades sex olika delar från koncepten fram. En grupp från Huddig och författaren Kristoffer Larsson tyckte dessa delar var bäst lämpade att gå vidare med. De delar som gick vidare var: − Konisk underdel − Kantig form − Dubbla rader med knappar på vänster konsol − Utåtlutande trängstyrning − Fram/back utåtlutande − Tvåhandsgrepp för trängstyrningen − Placering av stödbensreglage Utifrån dessa kommentarer och synpunkter på de framsållade koncepten skissade författaren fram fyra koncept som valdes att göras prototyper av. Skälet till att prototyper valdes att tillverkas var att det är svårt att känna och testa om ett koncept verkligen fungerar eller inte genom att bara kolla på en skiss. Målet med examensarbetet var att generera fram unika koncept men även att tillverka prototyper av dem, vilket uppnåddes. Utifrån resultat av denna rapport och prototyperna kan Huddig fortsätta att utveckla spakkonsolerna till en genomtänkt och smart lösning.Abstract The author Kristoffer Larsson wrote this examinations paper for the excavator loader company Huddig AB in Hudiksvall. The subject for this bachelor’s thesis is development of joystick pads at Huddig. The background for the bachelor's thesis is that Huddig have been during the last years developed and redesigning the interior of the cabin. The problem is that the joystick brackets haven’t followed the same development. The goal with this bachelor's thesis is to develop and manufacture four prototypes with consideration on design, ergonomics, bottom positions, control of steering, rototilt, choice of material and manufacturing method. To get a picture of what the drivers want and theirs aspect of the development of the joysticks pads the author did a market research with Huddigs customers. After the market research was done some methods and functions solving methods was used to break down the product to different functions. Eight different concepts were generated and the finial concepts were selected of a group from Huddig and Kristoffer Larsson. They selected the concepts because they taught that they were best suited to manufacture prototypes of. These are the subjects of the concepts: − Conic underpart − Angular design − Double rows with bottoms at left bracket − Tilted steering control − Tilted transport direction shifter − Two hand grip for steering − Placement of hydraulic lifters From these comments and aspects the author drew four sketches to have as guidelines for the prototypes. The reason to make prototypes was that it is hard to anticipate if a concept works in the real life based from a sketch. The goal with this bachelor's thesis was to design and manufacture innovated concepts which have been done. From the result of the bachelor's thesis Huddig can use it to continue to develop the joystick brackets to a successful product
Alternative Saccharomyces interspecies hybrid combinations and their potential for low-temperature wort fermentation
No full textThe lager yeast hybrid (Saccharomyces cerevisiae × Saccharomyces eubayanus) possesses two key characteristics that are essential for lager brewing: efficient sugar utilization and cold tolerance. Here we explore the possibility that the lager yeast phenotype can be recreated by hybridizing S. cerevisiae ale yeast with a number of cold-tolerant Saccharomyces species including Saccharomyces arboricola, Saccharomyces eubayanus, Saccharomyces mikatae and Saccharomyces uvarum. Interspecies hybrids performed better than parental strains in lager brewing conditions (12°C and 12°P wort), with the S. mikatae hybrid performing as well as the S. eubayanus hybrid. Where the S. cerevisiae parent was capable of utilizing maltotriose, this trait was inherited by the hybrids. A greater production of higher alcohols and esters by the hybrids resulted in the production of more aromatic beers relative to the parents. Strong fermentation performance relative to the parents was dependent on ploidy, with polyploid hybrids (3n, 4n) performing better than diploid hybrids. All hybrids produced 4-vinyl guaiacol, a smoke/clove aroma generally considered an off flavour in lager beer. This characteristic could however be eliminated by isolating spore clones from a fertile hybrid of S. cerevisiae and S. mikatae. The results suggest that S. eubayanus is dispensable when constructing yeast hybrids that express the typical lager yeast phenotype.Peer reviewe
Influence of valine and other amino acids on total diacetyl and 2,3-pentanedione levels during fermentation of brewer’s wort
Get PDFUndesirable butter-tasting vicinal diketones are produced as by-products of valine and isoleucine biosynthesis during wort fermentation. One promising method of decreasing diacetyl production is through control of wort valine content since valine is involved in feedback inhibition of enzymes controlling the formation of diacetyl precursors. Here, the influence of valine supplementation, wort amino acid profile and free amino nitrogen content on diacetyl formation during wort fermentation with the lager yeast Saccharomyces pastorianus was investigated. Valine supplementation (100 to 300 mg L−1) resulted in decreased maximum diacetyl concentrations (up to 37 % lower) and diacetyl concentrations at the end of fermentation (up to 33 % lower) in all trials. Composition of the amino acid spectrum of the wort also had an impact on diacetyl and 2,3-pentanedione production during fermentation. No direct correlation between the wort amino acid concentrations and diacetyl production was found, but rather a negative correlation between the uptake rate of valine (and also other branched-chain amino acids) and diacetyl production. Fermentation performance and yeast growth were unaffected by supplementations. Amino acid addition had a minor effect on higher alcohol and ester composition, suggesting that high levels of supplementation could affect the flavour profile of the beer. Modifying amino acid profile of wort, especially with respect to valine and the other branched-chain amino acids, may be an effective way of decreasing the amount of diacetyl formed during fermentation
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