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O-28 Genetics, ecology, and the diverse species Saccharomyces cerevisiae—Isolation of novel strains and lineages

Presenter: Rob J. Arnold, F&R Distilling Co., Fort Worth, TX

The budding yeast Saccharomyces cerevisiae has been associated with human activity for several millennia due to its use in a variety of processes, including the fermentation of alcoholic beverages. The species has also been intensively studied in the laboratory, being used as a model organism for genetics and molecular biology. It was the first eukaryote genome to be sequenced, and its 12 Mb genome is better annotated than any other eukaryotic organisms. The intensive research that surrounds S. cerevisiae has revealed surprising data that could prove groundbreaking with regard to the production of alcoholic beverages. In 2011, there were five known lineages of S. cerevisiae: wine/European, North American, Malaysian, West African, and sake. In the Western world, most industrial yeasts (brewing, winemaking, etc.) come from the wine/European lineage (Warringer et al., PlOS Genet., 2011). Data from the Warringer et. al. study revealed that each lineage possesses population-specific traits that are unique to one lineage. Traits (or phenotypes) result from the expression of an organism’s genes, and genes control the expression of proteins that facilitate the catabolism of wort components into ethanol and aroma compounds. Therefore, it can be argued that population-specific traits among lineages could result in either the production of novel aroma compounds or the production of already known aroma compounds at strikingly different concentrations than are normally observed. In 2012, a Chinese expedition revealed eight new lineages of S. cerevisiae that were unknown to science: CHN I–CHN VIII. Interestingly, CHN I was revealed to be ancestral to all known lineages, making China the proposed origin of the species. If the argument that lineages contain population-specific traits is true, the discovery of eight new lineages could produce a wealth of novel aromas to be incorporated into alcoholic beverages. Furthermore, when one considers that the Western world has only utilized one lineage industrially, there are at least 11 lineages that could be explored for beverage production. Indeed, at least some of the lineages other than wine/European are suitable for beverage alcohol fermentation, with the sake and West African lineages being used for the production of sake and African being used for wines and beer, respectively. In 2011, Firestone & Robertson’s Head Distiller Rob Arnold isolated 11 S. cerevisiae strains from a Texas pecan nut. One of these isolates, nicknamed Brazos, is the strain used at the distillery today. Although there is a North American lineage, all the strains within this lineage are unable to metabolize maltose. Arnold’s strain is very effective at maltose fermentation, leading him to believe that the strain could fit into an unknown or mosaic lineage. This oral presentation will cover topics on S. cerevisiae lineages, the potential of lineage diversity with regard to unique flavors in fermented beverages, and the data surrounding the Brazos strain pertaining to lineage and novel aroma compound production.

A native of Kentucky with a grandfather and multiple uncles who worked in the bourbon industry, Rob Arnold grew up surrounded by the distilling world. After graduating from the University of Tennessee with a bachelor’s degree in microbiology, he enrolled in a Ph.D program in biochemistry at UT Southwestern Medical Center at Dallas, where he studied microbial fermentation and analytical chemistry. Two years into the Ph.D. program, he was contemplating leaving the medical research field to open a distillery. While in the early fundraising stages of pursuing that goal, he learned of the Firestone & Robertson Distilling Co. from Fort Worth South— the development group with which both he and F&R were working. Rob contacted F&R and learned that they were in need of a head distiller. After meeting with Leonard Firestone and Troy Robertson, and realizing they all had similar visions for bringing whiskey to Fort Worth, Rob left school early with his master’s degree and joined the F&R team in 2011.