Flavor Tailoring for Future Brewing: Unleashing Brettanomyces Yeast Potential

Marc Serra Colomer*

*Corresponding author for this work

Research output: Book/ReportPh.D. thesis

Abstract

Yeast are essential organisms for the production of beer, due to their capability to perform alcoholic fermentation and produce flavours. Currently, beer production relies mainly on two single yeast species, Saccharomyces cerevisiae and Saccharomyces. pastorianus. Despite more than 2,000 yeast species having been identified, little is known about their potential application for brewing. This thesis focuses on exploring yeast diversity, in particular Brettanomyces species, for their potential for beer production. Brettanomyces species are already present in certain wine and beer fermentations, and they are typically recognised as spoilage yeast. The main reason is the production of volatile phenols, generally associated with undesired flavours. However, flavour
production by Brettanomyces species contributes positively to certain beer styles, such as lambics and saisons. Further investigation of flavour production on a genomic and metabolic level may allow the development of Brettanomyces strains with desired sensory profiles and of novel flavours in beverages. During this PhD project, Brettanomyces bruxellensis variants with altered production of volatile phenols were developed. The selected candidates were physiologically tested under controlled conditions. Production of volatile phenols was found to be highly dependent on the fermentation media, in particular on the sugar composition. Gene targets with a potential influence on volatile phenols production are suggested, such as BbSTL1 or BbVPH1. Moreover, properties such as betaglucosidase activity and nitrate assimilation were tested in a brewing context. We analysed these properties by performing fermentations in media with different hop additions. New insights in synergistic effects between hops and yeast were gained, and it could be concluded that genomic background strongly influences beta-glucosidase activity and nitrate assimilation. Furthermore, a
collection of Brettanomyces species from different origins was screened for brewing relevant properties. With the aid of next generation sequencing and bioinformatics analysis, we established a solid genotype-phenotype correlation in brewing relevant traits such as volatile phenol production, cellobiose degradation and maltose assimilation. In the same context, we identified several Brettanomyces strains that are suitable for brewing, possessing exclusive properties such as high ester production, high beta-glucosidase activity, deficient maltose utilisation and absence of volatile phenols production. Overall, the findings of this thesis broaden the knowledge of Brettanomyces species utilisation for brewing, particularly with regard to flavour production. Subsequently, the selection of the adequate yeast strain with a focus on the end-product is emphasized. Current and future directions of the use of Brettanomyces yeast in brewing are compiled, and the potential of exploring natural diversity for new product development is illustrated.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages119
Publication statusPublished - 2019

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