UC Davis Awarded Funding to Merge the Viticulture & Enology Wine Microbe Collection with the Phaff Yeast Culture Collection
For more than sixty years, two of the most important libraries of California microbiology have lived in separate departments on the UC Davis campus. Now, thanks to a grant from the American Vineyard Foundation and Washington Wine Commission, they're (re)uniting.
The grant to Ben Montpetit, Chair of Viticulture and Enology (VEN), and Chris Simmons, Chair of Food Science and Technology (FST) is to fund "Stabilization and Valorization of the UC Davis Wine Microbe Collection" — a project to transfer, validate, and permanently preserve the bulk of the VEN Wine microbe collection by merging it into the FST Phaff Yeast Culture Collection.
One Collection, Split by Time and Space
The story starts in Berkeley in the 1890s, when Frederic Bioletti, working for Eugene Hilgard, began isolating and cataloguing wine yeasts within a department that ultimately evolved into the UC Davis VEN and FST departments. William Cruess and Emil Mrak carried that work forward in the following decades, expanding the collection and helping California's wine industry rebuild after Prohibition ended in 1933. Herman Phaff joined the effort in 1944 and, over the next four decades, isolated and characterized more than 6,200 yeast strains, publishing over 300 papers on fermentation, food spoilage, and yeast taxonomy along the way. Generations of UC Davis students — many who went on to run California wineries — learned their yeast biology from Phaff himself.
In 1963, Ralph Kunkee joined the Department of Viticulture and Enology and began building his own wine-focused microbe collection, drawing on Phaff's original strains and adding his own. Bacteria used in malolactic fermentation, spoilage organisms like Brettanomyces, and hundreds of isolates from spontaneous wine fermentations and the department's Wine Microbiology Laboratory course all found a home there. Over time, the collections diverged — one focused broadly on yeast ecology and taxonomy, the other tightly focused on the practical needs of winemaking.
Today, the VEN collection holds roughly 3,370 strains of yeast, bacteria, and filamentous fungi, including a signature set of 197 Brettanomyces isolates that helped researchers build the field's first Brettanomyces aroma wheel, and a non-hydrogen-sulfide-producing Saccharomyces strain — pulled from the historic Robert Mortimer vineyard isolate collection — that was used to breed a sulfide-free yeast now sold commercially across the wine, beer, and coffee industries.
Why Now
Since the VEN collection's longtime curator Lucy Joseph retired in 2021, the collection has lacked a full time staff member to advance the use of the collection. Meanwhile, the people who hold the institutional memory of where these strains came from — Joseph and retired professor Linda Bisson — are, in the project's own words, still living nearby and willing to help, but not indefinitely. Kyria Boundy-Mills, who ran the Phaff collection for 25 years before retiring in December 2025, has agreed to volunteer her time to oversee the merger, drawing on the same playbook she used to successfully rescue three other yeast collections over the past decade.
"We understand that drivers for this merger are retirements and reduced funding support that threaten the long-term viability of both collections," Bisson and Joseph wrote in a letter of support. "Aligning the two collections under a unified management structure is the most efficient and sustainable way to ensure continuity of service."
What the Grant Will Do
Over three years, the project team — including interim Phaff Yeast Collection Manager Karen Kalanetra and a crew of undergraduate assistants — will inventory the VEN collection, extend provenance data through literature review and interviews with former curators, and renew, purify, and DNA-sequence roughly 1,300 priority yeast strains and 450 bacterial strains for public deposit. Novonesis, a global biosolutions company, will contribute in-kind genomic sequencing support to assist with species identification. The contribution is part of the company’s work with research institutions to strengthen scientific collaboration and expand knowledge of microbial diversity.Every validated strain will be triple-preserved: a working stock and backup stock at UC Davis, and a third shipped to the USDA's National Laboratory for Genetic Resource Preservation in Fort Collins, Colorado, for permanent safekeeping.
When complete, the merged collection will bring the Phaff catalog to over 13,000 yeast strains, cross-referenced under both their original VEN and new Phaff accession numbers, and searchable by any winery, researcher, or company that needs access to California's accumulated wine-microbe biodiversity. Notably, roughly 80% of the microbes in the collection are only available from the Phaff collection, solely owned by the University of California, and available for commercial licensing.
A Deep Well of Wild Saccharomyces
What sets this combined resource apart isn't just its size — it's the sheer depth of naturally occurring Saccharomyces it contains. Both collections are unusually rich in wild isolates rather than lab-generated strains: the VEN collection holds hundreds of S. cerevisiae strains pulled directly from spontaneous wine fermentations and native California vineyard and winery environments, while the founding Phaff collection was itself built on strains Herman Phaff and his predecessors gathered from wineries, breweries, other food and beverage fermentations, and natural habitats across North America, Europe and beyond. Together, they represent a truly impressive assembly of naturally occurring Saccharomyces genetic diversity. Recent licenses of UC Davis Saccharomyces strains include the low hydrogen sulfide wine strains developed by Bisson, and an acrylamide-reducing strain.
That depth of wild Saccharomyces diversity has value well beyond the wine industry. The genetic variation also fuels strain discovery in brewing, sake production, and industrial ethanol and biofuel fermentation — all of which depend on Saccharomyces strains selected for stress tolerance, flavor character, or fermentation efficiency. By consolidating the two collections under a single, actively curated catalog, this project doesn't just preserve wine heritage — it opens a much broader pool of natural Saccharomyces variation to researchers working on other Saccharomyces-driven fermentations, positioning the Phaff collection as a resource for the wider fermentation science community.
Science Funding That Hasn't Kept Pace
Grants like this one keep the work moving but sustaining these types of collections long-term requires sustained investment. While over 10,000 yeast strains in the current Phaff collection have been validated and made available to the public, nearly 8700 strains sit in a processing backlog for lack of support. A Phaff Yeast Collection Endowment was established in 2001 and currently provides around 3% of the annual costs required for the collection's staffing and maintenance needs. Needless to say, this endowment will need to grow significantly to address basic needs and realize the collection’s full potential.
To learn more about supporting the Phaff Yeast Culture Collection endowment, contact the Departments of Food Science and Technology or Viticulture and Enology at UC Davis or visit https://phaffcollection.ucdavis.edu/giving.