Citizen Science Unlocks the Diversity of Swedish Honey Yeast

Other conference contribution, 2024

Biological diversity is a vast, untapped resource of yeasts for biotechnological applications.  Over 100,000 yeast species are believed to exist in nature, but most remain unidentified. Once discovered, these yeasts can be harnessed as efficient microbial cell factories for sustainable production in a circular bioeconomy.

Honeybees, with their wide foraging range of up to 2–3 km from their hive, play a crucial role in our ecosystem. In addition to nectar and pollen, bees gather various microorganisms, which become a small but natural part of honey. Honey is a complex mixture of sugars, enzymes, and antimicrobial substances, and it imposes osmotic, oxidative, and low-pH stress on the microorganisms. As many of these stressors are also present in industrial bioprocesses, honey is projected as an excellent source for bioprospecting yeasts with cell factory potential.

In the summer of 2023, beekeepers from 100 different geographical locations in Sweden generously contributed honey samples, from which we isolated 2,500 unique honey yeast strains. The collection contains a wealth of diversity: we found yeasts belonging to 27 families and more than 70 species. Although our collection is dominated by species from the Starmerella, Zygosaccharomyces, Rhodotorula, Aureobasidium, Metschnikowia and Naganishia families that are known to be present in nectar, honey, and other bee products, we also find several yeasts that have not been found associated with honey before, as well as yeasts that likely represent new species.

Growth characterization of the honey yeasts shows that many strains are remarkably stress-tolerant, and most can grow at ≥60% sugar content. Moreover, many produce metabolites of significant biotechnological interest, such as microbial oils, surfactants, and polyols. As such, this citizen science project will shed light on yeast biodiversity in honey and lead to the identification and characterization of new yeasts with cell factory potential.