Hoppy beer is all the rage among craft brewers and beer lovers, and now a group of UC Berkeley researchers led by Charles Denby and Rachel Li have come up with a way to create these unique flavors and aromas without using hops.

The researchers created strains of brewer’s yeast that not only ferment the beer but also provide two of the prominent flavor notes provided by hops. The engineered yeast strains were altered using the CRISPR-Cas9 gene-editing tool. They inserted four new genes plus the promoters that regulate the genes into industrial brewer’s yeast.

Denby initially came to UC Berkeley to work on sustainable transportation fuels with Professor Jay Keasling, a pioneer in the field of synthetic biology. He started home brewing out of curiosity with a group of friends. “I was interested in (the) fermentation process. I found out that the molecules that give hops their hoppy flavor are terpene molecules, and it wouldn’t be too big of a stretch to think we could develop strains that make terpenes at the same concentrations that you get when you make beer and add hops to them.”

“The final hook was that a hoppy strain of yeast would make the brewing process more sustainable than using agriculturally produced hops, which is a very natural resource intensive product,” he said.