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A number of fungal isolates were recently obtained from a survey of the microbiota of multiple breweries and brewery products. Here, we sought to explore whether any of these brewery contaminants could be repurposed for beneficial use in beer fermentations, with particular focus on low‐alcohol beer. There were 56 yeast strains first screened for the utilization of different carbon sources, ability to ferment brewer's wort, and formation of desirable aroma compounds. A number of strains appeared maltose‐negative and produced desirable aromas without obvious off‐flavours. These were selected for further scaled‐up wort fermentations. The selected strains efficiently reduced wort aldehydes during fermentation, thus eliminating undesirable wort‐like off‐flavours, and produced a diverse volatile aroma profile. Two strains, Trigonopsis cantarellii and Candida sojae, together with a commercial Saccharomycodes ludwigii reference strain, were selected for 30‐L‐scale wort fermentations based on aroma profile and similarity to a commercial reference beer during sensory analysis using projective mapping. Both strains performed comparably to the commercial reference, and the T. cantarellii strain in particular, produced low amounts of off‐flavours and a significantly higher amount of the desirable monoterpene alcohol trans‐geraniol. The strain was also sensitive to common food preservatives and antifungal compounds and unable to grow at 37°C, suggesting it is relatively easily controllable in the brewery, and appears to have low risk of pathogenicity. This study shows how the natural brewery microbiota can be exploited as a source of non‐conventional yeasts for low‐alcohol beer production. [ABSTRACT FROM AUTHOR]

Abstract: The 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. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A combination of biological and non-biological factors has led to the interspecific hybrid yeast species Saccharomyces pastorianus becoming one of the world's most important industrial organisms. This yeast is used in the production of lager-style beers, the fermentation of which requires very low temperatures compared to other industrial fermentation processes. This group of organisms has benefited from both the whole-genome duplication in its ancestral lineage and the subsequent hybridization event between S. cerevisiae and S. eubayanus, resulting in strong fermentative ability. The hybrid has key traits, such as cold tolerance and good maltose- and maltotriose-utilizing ability, inherited either from the parental species or originating from genetic interactions between the parent genomes. Instability in the nascent allopolyploid hybrid genome may have contributed to rapid evolution of the yeast to tolerate conditions prevalent in the brewing environment. The recent discovery of S. eubayanus has provided new insights into the evolutionary history of S. pastorianus and may offer new opportunities for generating novel industrially-beneficial lager yeast strains. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Flavours are biologically active molecules of large commercial interest in the food, cosmetics, detergent and pharmaceutical industries. The production of flavours can take place by either extraction from plant materials, chemical synthesis, biological conversion of precursor molecules or de novo biosynthesis. The latter alternatives are gaining importance through the rapidly growing fields of systems biology and metabolic engineering, giving efficient production hosts for the so-called 'bioflavours', which are natural flavour and/or fragrance compounds obtained with cell factories or enzymatic systems. Yeasts are potential production hosts for bioflavours. In this mini-review, we give an overview of bioflavour production in yeasts from the process-engineering perspective. Two specific examples, production of 2-phenylethanol and vanillin, are used to illustrate the process challenges and strategies used. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A screen of 14 S. pastorianus lager-brewing strains showed as much as a nine-fold difference in wort total diacetyl concentration at equivalent stages of fermentation of 15°Plato brewer's wort. Two strains (A153 and W34), with relatively low and high diacetyl production, respectively, but which did not otherwise differ in fermentation performance, growth or flavour production, were selected for further investigation. Transcriptional analysis of key genes involved in valine biosynthesis showed differences between the two strains that were consistent with the differences in wort diacetyl concentration. In particular, the ILV6 gene, encoding a regulatory subunit of acetohydroxy acid synthase, showed early transcription (only 6 h after inoculation) and up to five-fold greater expression in W34 compared to A153. This earlier transcription was observed for both orthologues of ILV6 in the S. pastorianus hybrid ( S. cerevisiae × S. eubayanus), although the S. cerevisiae form of ILV6 in W34 also showed a consistently higher transcript level throughout fermentation relative to the same gene in A153. Overexpression of either form of ILV6 (by placing it under the control of the PGK1 promoter) resulted in an identical two-fold increase in wort total diacetyl concentration relative to a control. The results confirm the role of the Ilv6 subunit in controlling α-acetolactate/diacetyl concentration and indicate no functional divergence between the two forms of Ilv6. The greater contribution of the S. cerevisiae ILV6 to acetolactate production in natural brewing yeast hybrids appears rather to be due to higher levels of transcription relative to the S. eubayanus form. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Two distinct genetic groups (Saaz and Frohberg) exist within the hybrid Saccharomyces pastorianus ( S. cerevisiae × S. eubayanus) taxon. However, physiological/technological differences that exist between the two groups are not known. Fermentative capability of the parental S. eubayanus has likewise never been studied. Here, 58 lager strains were screened to determine which hybrid group they belonged to, and selected strains were characterized to determine salient characteristics. In 15 °P all-malt wort fermentations at 22 °C, Frohberg strains showed greater growth and superior fermentation (80% apparent attenuation, 6.5% alcohol by volume in 3-4 days) compared to all other strains and maintained highest viability values (>93%). Fermentation with S. eubayanus was poor at the same temperature (33% apparent attenuation, 2.7% alcohol by volume at 6 days and viability reduced to 75%). Saaz strains and S. eubayanus were the least sensitive to cold (10 °C), though this did not translate to greater fermentation performance. Fermentation with S. eubayanus was poor at 10 °C but equal to or greater than that of the Saaz strains. Performance of Saaz yeast/ S. eubayanus was limited by an inability to use wort maltotriose. [14C]-Maltotriose transport assays also showed negligible activity in these strains (≤0.5 µmol min−1 g−1 dry yeast). Beers from Saaz fermentations were characterized by two- to sixfold lower production of the flavour compounds methyl butanol, ethyl acetate and 3-methylbutyl acetate compared to Frohberg strains. Higher alcohol and ester production by S. eubayanus was similar to that of Frohberg strains. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]