Harnessing heterosis: Enhancing industrial yeast functionality through interspecific hybridisation

Research output: ThesisDissertation

Abstract

Industrial fermentations of beer, cider and wine, can be very challenging for the yeast. Brewer's wort mainly comprises starch-derived sugars requiring specific transmembrane transporters. Apple and grape musts contain simpler sugars but with high fructose-to-glucose ratio and very high total sugar concentration, respectively. Additionally, environmental conditions, such as fermentation temperature, can hinder yeast performance. The temperature directly impacts the aromatic properties of a fermented beverage. Clean and fresh lager beer is a result of cold fermentation, only possible with the use of the hybrid yeast. Saccharomyces pastorianus combines the cold tolerant Saccharomyces eubayanus with good fermenter Saccharomyces cerevisiae. Genetically, lager yeast can be divided into two subgroups with different ratios of the parental DNA. Historically, these group differentiation matched the strains variable use of maltotriose.

In order to study maltotriose utilisation in lager yeast, the brewing performance of a diverse group of strains was linked to the uptake rates and presence of specific transporters. Contrary to the traditional characterisation, group I comprises strains with varying ability to consume maltotriose, enabled by the presence of SeAGT1 and MTT1 transporters. A58, a variant of the group I strain CBS1513, had a particularly high capacity to take up maltotriose, even at extreme temperatures (0°C). This property is a result of increased MTT1 copy number. The presence/absence of specific permeases accounts for much of the variation in lager yeast fermentation behaviour.

Besides variable sugar utilisation rates, lager yeast are phenotypically fairly homogeneous. The use of genetic modification in brewing yeast is not well accepted, limiting the possibilities for strain improvement. However, the discovery of S. eubayanus, raised the possibility to create new tailor-made lager yeast. By mating a domesticated ale strain with S. eubayanus hybrids were obtained with faster fermentation and superior alcohol content at low temperature (12°C). The main contribution of S. eubayanus to these new hybrid strains seems to be cold tolerance.

Yeast cryotolerance is also important in cider and wine making. Therefore, S. eubayanus was crossed with a S. cerevisiae wine-producing strain and the hybrids tested for their suitability for cider and wine making. In cider fermentation, hybrids maintained the superior fermentation rate of S. eubayanus without the unpleasant sulphur by-products generated by this parent. A consumer panel rated the ciders fermented with hybrid strains as identical to the wine strain cider. Both being significantly more pleasant than S. eubayanus' cider. The best performing hybrid was processed in active dry yeast form, and tested in winemaking conditions. The hybrid retained high viability and fermentation profile comparable to commercial strains but with increased production of pleasant aroma volatiles.

This project showed that interspecific hybridisation is an effective approach to improve low-temperature fermentation performance without compromising product quality.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Bankar, Sandip, Supervisor, External person
  • Gibson, Brian, Advisor
  • Ojamo, Heikki, Advisor, External person
Award date5 Dec 2018
Publisher
Print ISBNs978-952-60-8321-6
Electronic ISBNs978-952-60-8322-3
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

interspecific hybridization
heterosis
ciders
yeasts
fermentation
brewers yeast
maltotriose
winemaking
sugars
transporters
wines
brewing
temperature
beers
Saccharomyces cerevisiae
wort (brewing)
Saccharomyces
fermenters
genetic engineering
cold tolerance

Keywords

  • Saccharomyces eubayanus
  • hybrid
  • heterosis
  • cryotolerance
  • beer
  • cider
  • wine

Cite this

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title = "Harnessing heterosis: Enhancing industrial yeast functionality through interspecific hybridisation",
abstract = "Industrial fermentations of beer, cider and wine, can be very challenging for the yeast. Brewer's wort mainly comprises starch-derived sugars requiring specific transmembrane transporters. Apple and grape musts contain simpler sugars but with high fructose-to-glucose ratio and very high total sugar concentration, respectively. Additionally, environmental conditions, such as fermentation temperature, can hinder yeast performance. The temperature directly impacts the aromatic properties of a fermented beverage. Clean and fresh lager beer is a result of cold fermentation, only possible with the use of the hybrid yeast. Saccharomyces pastorianus combines the cold tolerant Saccharomyces eubayanus with good fermenter Saccharomyces cerevisiae. Genetically, lager yeast can be divided into two subgroups with different ratios of the parental DNA. Historically, these group differentiation matched the strains variable use of maltotriose. In order to study maltotriose utilisation in lager yeast, the brewing performance of a diverse group of strains was linked to the uptake rates and presence of specific transporters. Contrary to the traditional characterisation, group I comprises strains with varying ability to consume maltotriose, enabled by the presence of SeAGT1 and MTT1 transporters. A58, a variant of the group I strain CBS1513, had a particularly high capacity to take up maltotriose, even at extreme temperatures (0°C). This property is a result of increased MTT1 copy number. The presence/absence of specific permeases accounts for much of the variation in lager yeast fermentation behaviour. Besides variable sugar utilisation rates, lager yeast are phenotypically fairly homogeneous. The use of genetic modification in brewing yeast is not well accepted, limiting the possibilities for strain improvement. However, the discovery of S. eubayanus, raised the possibility to create new tailor-made lager yeast. By mating a domesticated ale strain with S. eubayanus hybrids were obtained with faster fermentation and superior alcohol content at low temperature (12°C). The main contribution of S. eubayanus to these new hybrid strains seems to be cold tolerance. Yeast cryotolerance is also important in cider and wine making. Therefore, S. eubayanus was crossed with a S. cerevisiae wine-producing strain and the hybrids tested for their suitability for cider and wine making. In cider fermentation, hybrids maintained the superior fermentation rate of S. eubayanus without the unpleasant sulphur by-products generated by this parent. A consumer panel rated the ciders fermented with hybrid strains as identical to the wine strain cider. Both being significantly more pleasant than S. eubayanus' cider. The best performing hybrid was processed in active dry yeast form, and tested in winemaking conditions. The hybrid retained high viability and fermentation profile comparable to commercial strains but with increased production of pleasant aroma volatiles. This project showed that interspecific hybridisation is an effective approach to improve low-temperature fermentation performance without compromising product quality.",
keywords = "Saccharomyces eubayanus, hybrid, heterosis, cryotolerance, beer, cider, wine",
author = "Frederico Magalhaes",
year = "2018",
language = "English",
isbn = "978-952-60-8321-6",
series = "Aalto University Publication Series: Doctoral Dissertations",
publisher = "Aalto University",
number = "237/2018",
address = "Finland",
school = "Aalto University",

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TY - THES

T1 - Harnessing heterosis

T2 - Enhancing industrial yeast functionality through interspecific hybridisation

AU - Magalhaes, Frederico

PY - 2018

Y1 - 2018

N2 - Industrial fermentations of beer, cider and wine, can be very challenging for the yeast. Brewer's wort mainly comprises starch-derived sugars requiring specific transmembrane transporters. Apple and grape musts contain simpler sugars but with high fructose-to-glucose ratio and very high total sugar concentration, respectively. Additionally, environmental conditions, such as fermentation temperature, can hinder yeast performance. The temperature directly impacts the aromatic properties of a fermented beverage. Clean and fresh lager beer is a result of cold fermentation, only possible with the use of the hybrid yeast. Saccharomyces pastorianus combines the cold tolerant Saccharomyces eubayanus with good fermenter Saccharomyces cerevisiae. Genetically, lager yeast can be divided into two subgroups with different ratios of the parental DNA. Historically, these group differentiation matched the strains variable use of maltotriose. In order to study maltotriose utilisation in lager yeast, the brewing performance of a diverse group of strains was linked to the uptake rates and presence of specific transporters. Contrary to the traditional characterisation, group I comprises strains with varying ability to consume maltotriose, enabled by the presence of SeAGT1 and MTT1 transporters. A58, a variant of the group I strain CBS1513, had a particularly high capacity to take up maltotriose, even at extreme temperatures (0°C). This property is a result of increased MTT1 copy number. The presence/absence of specific permeases accounts for much of the variation in lager yeast fermentation behaviour. Besides variable sugar utilisation rates, lager yeast are phenotypically fairly homogeneous. The use of genetic modification in brewing yeast is not well accepted, limiting the possibilities for strain improvement. However, the discovery of S. eubayanus, raised the possibility to create new tailor-made lager yeast. By mating a domesticated ale strain with S. eubayanus hybrids were obtained with faster fermentation and superior alcohol content at low temperature (12°C). The main contribution of S. eubayanus to these new hybrid strains seems to be cold tolerance. Yeast cryotolerance is also important in cider and wine making. Therefore, S. eubayanus was crossed with a S. cerevisiae wine-producing strain and the hybrids tested for their suitability for cider and wine making. In cider fermentation, hybrids maintained the superior fermentation rate of S. eubayanus without the unpleasant sulphur by-products generated by this parent. A consumer panel rated the ciders fermented with hybrid strains as identical to the wine strain cider. Both being significantly more pleasant than S. eubayanus' cider. The best performing hybrid was processed in active dry yeast form, and tested in winemaking conditions. The hybrid retained high viability and fermentation profile comparable to commercial strains but with increased production of pleasant aroma volatiles. This project showed that interspecific hybridisation is an effective approach to improve low-temperature fermentation performance without compromising product quality.

AB - Industrial fermentations of beer, cider and wine, can be very challenging for the yeast. Brewer's wort mainly comprises starch-derived sugars requiring specific transmembrane transporters. Apple and grape musts contain simpler sugars but with high fructose-to-glucose ratio and very high total sugar concentration, respectively. Additionally, environmental conditions, such as fermentation temperature, can hinder yeast performance. The temperature directly impacts the aromatic properties of a fermented beverage. Clean and fresh lager beer is a result of cold fermentation, only possible with the use of the hybrid yeast. Saccharomyces pastorianus combines the cold tolerant Saccharomyces eubayanus with good fermenter Saccharomyces cerevisiae. Genetically, lager yeast can be divided into two subgroups with different ratios of the parental DNA. Historically, these group differentiation matched the strains variable use of maltotriose. In order to study maltotriose utilisation in lager yeast, the brewing performance of a diverse group of strains was linked to the uptake rates and presence of specific transporters. Contrary to the traditional characterisation, group I comprises strains with varying ability to consume maltotriose, enabled by the presence of SeAGT1 and MTT1 transporters. A58, a variant of the group I strain CBS1513, had a particularly high capacity to take up maltotriose, even at extreme temperatures (0°C). This property is a result of increased MTT1 copy number. The presence/absence of specific permeases accounts for much of the variation in lager yeast fermentation behaviour. Besides variable sugar utilisation rates, lager yeast are phenotypically fairly homogeneous. The use of genetic modification in brewing yeast is not well accepted, limiting the possibilities for strain improvement. However, the discovery of S. eubayanus, raised the possibility to create new tailor-made lager yeast. By mating a domesticated ale strain with S. eubayanus hybrids were obtained with faster fermentation and superior alcohol content at low temperature (12°C). The main contribution of S. eubayanus to these new hybrid strains seems to be cold tolerance. Yeast cryotolerance is also important in cider and wine making. Therefore, S. eubayanus was crossed with a S. cerevisiae wine-producing strain and the hybrids tested for their suitability for cider and wine making. In cider fermentation, hybrids maintained the superior fermentation rate of S. eubayanus without the unpleasant sulphur by-products generated by this parent. A consumer panel rated the ciders fermented with hybrid strains as identical to the wine strain cider. Both being significantly more pleasant than S. eubayanus' cider. The best performing hybrid was processed in active dry yeast form, and tested in winemaking conditions. The hybrid retained high viability and fermentation profile comparable to commercial strains but with increased production of pleasant aroma volatiles. This project showed that interspecific hybridisation is an effective approach to improve low-temperature fermentation performance without compromising product quality.

KW - Saccharomyces eubayanus

KW - hybrid

KW - heterosis

KW - cryotolerance

KW - beer

KW - cider

KW - wine

M3 - Dissertation

SN - 978-952-60-8321-6

T3 - Aalto University Publication Series: Doctoral Dissertations

PB - Aalto University

ER -