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New Yeast Discovered at USciences Cuts Time for Sour Beer Production

By Brian Kirschner

Dr. Matthew J. Farber
Dr. Mathew J. Farber

A new yeast species discovered by University of the Sciences researcher Matthew J. Farber, PhD, promises to brew sour beer in half the time of the usual fermentation process. Named GY7B, the novel, lactic-acid producing yeast is capable of fermenting a pleasant, aromatic sour beer and eliminates a secondary fermentation process using bacteria that is normally required for production.

“We have evidence that GY7B is a novel yeast species with distinct characteristics,” said Dr. Farber, director of the brewing science certificate program and an assistant professor of biology. “In addition to the faster brewing time for sour beer, because the yeast itself makes lactic acid, there is no need for brewers to introduce bacteria to their production line thus avoiding contamination concerns. Plus, it’s delicious.”

In normal sour beer production, two steps are required to achieve its flavor. The first being a fermentation process by traditional brewer’s yeast, followed by the introduction of bacteria that ferments remaining sugars into lactic acid. The production time can be four-to-six weeks or longer. The GY7B yeast species delivers highly attenuated (~95%) fermentation which yields beers with bright lactic acidity balanced by a slight sweetness from glycerol produced during fermentation. The tartness of the beer is perfectly balanced with a pleasant bouquet of apple esters with no discernible off-flavors. 

Beer and Brewing
A Surprise in the Yeast: A brewing program in Philadelphia has come across a wild yeast that not only flocculates clear but also naturally produces lactic acid. Is GY7B the next big thing for sour beer? Beer and Brewing Magazine’s John Holl reported on the finding and came to campus to taste the beer and interview Dr. Farber.

The wild yeast was locally isolated on a tree near campus in West Philadelphia as an outcome of student research in Dr. Farber’s lab. Once cultured, GY7B went through production trials in the USciences pilot brewery and is the basis of ongoing research. The resulting analysis indicated the quite rare trait of heterolactic acid fermentation by yeast, something classically described in bacteria such as Lactobacillus and Pediococcus.

While sour beer is not widely found on shelves, Dr. Farber attributes that to the long fermentation time and the complexity and risks associated with its production. Both of which are addressed with this yeast species. 

“Our ultimate goal is to provide GY7B to a commercial yeast supplier who would in turn get it into the hands of more brewers,” said Dr. Farber. The application of the GY7B yeast for sour beer production is protected by provisional patent that was filed with the assistance of Domingos Silva, PhD, JD, of Saul Ewing Arnstein & Lehr, LLP.

For more information on GY7B, visit

Categories: News, Research, Misher College, Department of Biology, Biology, Brewing Science