Christopher Butler,* Linda Bisson, Vidhya Ramakrishnan, and Lucy Joseph 
*Department of Viticulture and Enology, University of California, Davis, CA 95616 (crbutler@ucdavis.edu)

Commonly known as “ferocious lactobacilli,” Lactobacillus kunkeei represents a unique threat to wine quality due to its ability to rapidly produce high concentrations of acetic acid and induce a [GAR+] prion state in Saccharomyces yeast. High levels of acetic acid can reduce yeast viability and wine quality, while a [GAR+] prion state alters the ability of Saccharomyces to exclusively consume glucose and fructose sugars. Individually or in combination, these conditions can lead to stuck or sluggish fermentations. The source of L. kunkeei spoilage in wine is currently unknown. However, recent studies of the microbial ecology of honeybees (Apis sp.) has revealed L. kunkeei as the dominant microbial constituent of the gut microbiome of multiple species. Located in the foregut and crop of the honeybee, L. kunkeei acts synergistically with other microorganisms to enhance the innate immune system of the honeybee, inhibiting the growth of a variety of pathogenic and non-pathogenic organisms, some of which are associated with Colony Collapse Disorder. Given the abundance of L. kunkeei in the honeybee gut microbiome, we hypothesized that these domesticated and native pollinators may act as a vector for L. kunkeei in grape juice, resulting in wine spoilage and reduced fermentation efficiency. Fifteen strains of L. kunkeei were isolated from 28 honeybee samples and inoculated into small-scale fermentations of Chardonnay juice. Of the 15 L. kunkeei isolates, 13 grew well in 2016 Chardonnay juice. We hypothesize that L. kunkeei isolated from honeybees will cause stuck or slugglish fermentations, similar to the fermentation kinetics observed by our lab with L. kunkeei UCD26 strain in 2015 Chardonnay. Preliminary studies have shown that when compared to a control group, many strains of L. kunkeei isolated from honeybees possess inhibitory action towards yeast fermentation similar to that of the L. kunkeei UCD26 strain.

Funding Support: American Vineyard Foundation, Paul Monk Scholarship, Adolf L. & Richie C. Heck Research Fellowship, The Wine Spectator Scholarship