Designing New Yeasts for Craft Brewing: When Natural Biodiversity Meets Biotechnology

Abstract

Beer is a fermented beverage with a history as old as human civilization and its productive process has been spread all around the world becoming unique in every country and iconic of entire populations. Ales and lagers are by far the most common beers; however, the combination of raw materials, manufacture techniques and aroma profiles are almost infinite, so it is not surprising to notice that there is a large amount of different beer styles, each of them with unique characteristics. Nowadays, diversification is becoming increasingly important in the brewing market and the brewers are continuously interested in improving and extending the already wide range of products, especially in craft brewery. One of the major components that can have a deep impact on the final product is yeast, since it is able to convert carbohydrates in wort, especially maltose and maltotriose, into ethanol, carbon dioxide and other minor aroma-active compounds. Saccharomyces cerevisiae (top‐fermenting yeasts used to produce ales) and Saccharomyces pastorianus (cryotolerant bottom‐fermenting hybrids between S. cerevisiae and Saccharomyces eubayanus responsible for the fermentation of lagers) are most used in breweries. However, an increasing number of different yeast starter cultures are commercially available, to improve the production efficiency also at relative low temperatures and to obtain desirable and diversified aroma profiles avoiding undesired compounds. Four main genetic engineering-free trends are becoming popular in craft brewing yeast development: 1) the research for novel reservoirs as source of new performant S. cerevisiae yeasts; 2) the creation of synthetic hybrids between S. cerevisiae and Saccharomyces non-cerevisiae in order to mimic lager yeasts by expanding their genetic background; 3) the exploitation of evolutionary engineering approaches; 4) the usage of non-Saccharomyces yeasts either in co-coculture or in sequential fermentation with S. cerevisiae. In the present work we summarized pro and contra of these approaches and provided an overview on the most recent advances on how brewing yeast genome evolved and domestication took place. Finally, we delineated how the correlations maps between genotypes and relevant brewing phenotypes can assist and further improve the search for novel craft beer starter yeasts.

Craft beer: An overview

“…Regarding the development of yeasts for craft brewing, the craft beer trends that are gaining popularity include: the research of new performant Saccharomyces cerevisiae yeasts; the creation of S. cerevisiae ‐ Saccharomyces non‐ cerevisiae synthetic hybrids with attitudes similar to those of lager yeasts; and the application of wild or selected non‐ Saccharomyces yeasts alone, or in cococulture or sequential fermentation with S. cerevisiae for the brewing of sour craft beer (Iattici, Catallo, & Solieri, 2020). The decision to use non‐ Saccharomyces yeasts is related to the aim of better modulate pH, the content in organic acids, volatile compounds, and other compounds deriving from yeast metabolic pathway, so changing the sensory characteristics of the resulting beers.…”

Never Change a Brewing Yeast? Why Not, There Are Plenty to Choose From

“…Interestingly enough that these techniques were initially developed by the brewing industry, when Øjvind Winge discovered the sexual cycle of S. cerevisiae and used his knowledge to combine desirable brewing traits by crossing different strains at the Carlsberg Research Laboratory in the 1930s ( Winge, 1935 ; Barnett, 2007 ). So the brewing industry could end up renewing their applied yeast research and their strain portfolio by going back to their own roots ( Gibson et al, 2017 ; Iattici et al, 2020 ).…”

“…A vast number of so-called nonconventional yeasts have been isolated from these mixed fermentations over the years and their impact on fermentation performance and flavor profiles has been studied ( Spencer et al, 2002 ; Michel et al, 2016a ; Varela, 2016 ; Gibson et al, 2017 ; Capece et al, 2018b ; Holt et al, 2018 ; Canonico et al, 2019 ; Colomer et al, 2019 ; Cubillos et al, 2019 ). In addition to using pure yeast cultures from these nonconventional yeast species in brewing of novel beer styles or special beers ( Steensels et al, 2015 ; Michel et al, 2016b ; Capece et al, 2018a ; De Francesco et al, 2018 ; Gutiérrez et al, 2018 ; Ravasio et al, 2018 ; Colomer et al, 2020 ; Iattici et al, 2020 ; Zdaniewicz et al, 2020 ), these yeasts could be used, where genetically possible, to expand the concept of novel interspecies hybrids for the brewing industry beyond the Saccharomyces genus adding even more genetic diversity to brewer’s yeasts.…”

Hybridization of <em>Saccharomyces cerevisiae</em> Sourdough Strains with Cryotolerant <em>Saccharomyces bayanus</em> NBRC1948 as a Strategy to Increase Diversity of Strains Available for Lager Beer Fermentation

“…Bioprospecting efforts in brewing seek to utilize yeasts from environments other than the brewery in order to augment and/or diversify flavor properties of the final product [38]. Sourdough is a bio-reservoir of particular interest due to the occurrence of maltose-positive S. cerevisiae strains with QPS/GRAS status [27,59] and potentially well-accepted by consumers for their provenience from an artisanal food system [60]. The search for new S. cerevisiae sourdough strains as wild stocks could have great potential for wheat and other speciality beers [34,39].…”