Two novel strains of Torulaspora delbrueckii isolated from the honey bee microbiome and their use in honey fermentation

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.

An organoleptic survey of meads made with lactic acid-producing yeasts

“…The LAY strains tested here tended to attenuate mead less than they do beer wort (17,28), with L. thermotolerans strain YH27 yielding the highest attenuation, finishing with an ABV of 10.2%. H. vineae strain YH72 had the lowest attenuation, with an ABV of 4.2%, which is in stark contrast to our recent work with YH72 in mead production that yielded a finished product with 8.2% ABV (17). The reason for this discrepancy is currently unknown but could be due to variations in the honey musts used between experiments or the yeast nutrient supplementation regime used here.…”

“…1A,B). This was not unexpected because WLP715 is an industrial strain known for its high levels of attenuation (15), while the LAY have displayed variable levels of attenuation of beer wort (14) and mead (17). Although all 15 meads had a final pH of 3.70 or below, those made with LAY were significantly more acidic on average ( p = 0.0004; Fig.…”