Abstract
Yeasts are ubiquitous microbes found in virtually all environments. Many yeast species can ferment sugar into ethanol and CO2, and humans have taken advantage of these characteristics to produce fermented beverages for thousands of years. As a naturally abundant source of fermentable sugar, honey has had a central role in such fermentations since Neolithic times. However, as beverage fermentation has become industrialized, the processes have been streamlined, including the narrow and almost exclusive usage of yeasts in the genus Saccharomyces for fermentation. We set out to identify wild honey- or honey-bee-related yeasts that can be used in honey fermentation. Here, we isolated two strains of Torulaspora delbrueckii from the gut of a locally collected honey bee. Both strains were able to ferment honey sugar into mead but failed to metabolize more than a modest amount of wort sugar in trial beer fermentations. Further, the meads fermented by the T. delbrueckii strains displayed better sensory characteristics than mead fermented by a champagne yeast. The combination of T. delbrueckii and champagne yeast strains was also able to rapidly ferment honey at an industrial scale. Thus, wild yeasts represent a largely untapped reservoir for the introduction of desirable sensory characteristics in fermented beverages such as mead.
Highlights
Mankind has been fermenting foods and beverages for thousands of years [1,2,3,4], which certainly predates our knowledge that yeasts were the microbial agents responsible for metabolizing sugar into alcohol
Honey, which is produced by honey bees such as Apis mellifera, is a natural source of abundant, readily fermentable sugar and has been found as an ingredient in some of the earliest known fermented beverages [2]
T. delbrueckii YH178 and YH179 were successfully used in mixed honey fermentations with S. cerevisiae WLP715 on a production scale. These data suggest that T. delbrueckii YH178 and YH179 have beneficial honey fermentation profiles and are suitable for mead production by homebrewers and professional mead makers
Summary
Mankind has been fermenting foods and beverages for thousands of years [1,2,3,4], which certainly predates our knowledge that yeasts were the microbial agents responsible for metabolizing sugar into alcohol. In the case of mead, it is often relatively simple to utilize locally produced honey, but few meaderies use indigenous microbes unless they rely on those naturally found in the honey itself Such microbes are naturally resistant to high osmotic stress from concentrated sugar in honey and typically come from pollen/flower, bee gut microbiome, and dirt/dust contamination of the honey (reviewed in [12,13]). These organisms include multiple species from dozens of different genera of bacteria (e.g., Bacillus, Citrobacter, and Lactobacillus), yeast (e.g., Saccharomyces, Schizosaccharomyces, and Pichia), and molds. These data suggest that T. delbrueckii YH178 and YH179 have beneficial honey fermentation profiles and are suitable for mead production by homebrewers and professional mead makers
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