Researchers have created a new yeast stream, which could mean the end of hops in beer. Charles Denby and Rachel Li, two former scientist from the University of California, Berkeley, have used DNA-editing software to splice genes from mint and basil plants into yeast cells. They have recently launched a startup called Berkeley Brewing Science to market these hoppy yeasts to brewers . The genetically modified yeast does not only ferment the beer but also provide linalool and geraniol, two of the prominent hops flavor notes.
Charles Bamforth, a malting and brewing authority at UC Davis, brewed a beer from three of the most promising strains, and conducted a double-blind taste tests at Lagunitas Brewing Company in Petaluma, California.
28 tasters characterized beer made from the engineered strains as more hoppy than a control beer made with regular yeast and Cascade hops. Bryan Donaldson, innovations manager at Lagunitas, described the taste of the beer, which was produced with the modified yeast, as “fruit loops and orange blossom”, with no discernible “off-flavours”.
Will this mean the end of hops in beer? Thomas Becker, who holds the chair of brewing and drinks technology at the renowned Technical University Munich-Weihenstephan, says that in theory this method would allow to reduce hops in beer. But he says, said a wider usage of this method is not very likely amongst brewers, given the fact that more and more breweries increased their usage of aroma hops in the last years, not just to increase the bitterness in beer but to give it a distinct aroma profile.
And Becker adds that genetically modified raw materials and organisms are not allowed in beer according to the over 500 year-old German Purity Law of beer. So, even if the whole world will brew beer without hops, the hop gardens in Bavaria will still produce the raw material for the German beers.
This discussion will not stop the American researchers.
“We started our work on engineering microbes to produce isoprenoids—like flavors, fragrances, and artemisinin—about 20 years ago,” said Jay Keasling, a pioneer in the field of synthetic biology and a professor of chemical and biomolecular engineering.
Denby, who came to UC Berkeley to work on sustainable transportation fuels, learned here how to make microbes, primarily bacteria and yeast, ramp up their production of complex molecules called terpenes, and then insert genes that turn these terpenes into commercial products.
These microbes can make such chemicals as the antimalarial drug, artemisinin, fuels such as butanol, and aromas and flavors used in the cosmetic industry, but the brewing project “found me,” Denby, a passonate home-brewer, said.
“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,” he added.
Denby and Li inserted all of the genetic components—a CRISPR-Cas9 gene, which serves as a simple and inexpensive gene-editing tool, four yeast, mint, and basil genes, and promoters—into yeast on a tiny circular DNA plasmid. The yeast cells then translated the Cas9 gene into the Cas9 proteins, which cut the yeast DNA at specific points. Yeast repair enzymes then spliced in the four genes plus promoters.
“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,” Denby explained.
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 says.
