Charles Denby is a biochemist at UC Berkeley, co-first author of the paper, and founder of Berkeley Brewing Science, a beer startup that hopes to offer breweries a more sustainable way to brew hop-forward craft beers using genetically engineered yeast.
Denby told Seeker that he stumbled into brewing science through a combination of his Ph.D. research into sustainable biofuels and a weekend home-brewing hobby. He did his postdoctoral work in the lab of Jay Keasling, a pioneer of engineering microbes that consume renewable feedstock and spit out useful chemicals like diesel fuel or fragrance molecules for the cosmetics industry.
Reading up on the chemistry of hops, Denby figured out that the flavor molecules that give hops their grapefruity taste belong to the same class of molecules, known as terpenes, that he was already producing in Keasling’s lab.
“When you open a bottle of craft beer, or pour it from a tap, these terpene molecules will volatilize and hit your nose and hit your palette, and that’s why they impart such strong flavors,” said Denby.
RELATED: Human Immunity to Cas9 Could Threaten CRISPR’s Future
Two terpene molecules in particular are found in abundance in the essential oils that give hops their zesty, bitter taste: linalool and geraniol. With his bioengineering experience, Denby knew that it was possible, though difficult, to isolate the genes that code for those two flavor molecules and insert them into brewer’s yeast, the microbe responsible for fermenting barley into beer.
Denby couldn’t steal the genes directly from hops, because plant geneticists don’t know which snippets of hops DNA code for those flavor molecules. Instead, he and his research partner Rachel Li copied genes from mint and basil that encode for the enzymes that produce linalool and geraniol.
Then it was time to let CRISPR do its thing. The Berkeley researchers created a DNA package that included the mint and basil genes plus some yeast genes that acted as “promoters” controlling the amount of each enzyme that would be produced during fermentation. The package was inserted into the genome of standard brewer’s yeast using CRISPR’s genetic “scissors.”
Denby and Li didn’t just engineer one strain of hoppy yeast. They created 48 different varieties, each with a different combination of promoters that activated the enzymes at different levels and different times in the fermentation process. They then brewed 48 tiny test batches of beer to measure the amount of the flavor molecules in the final product.
Once they picked the four top varieties, it was time for the taste test.
The Berkeley team brought their engineered beer to the Lagunitas Brewing Company in Petaluma, California, where 27 brewery employees sat down for a blind taste test between the yeast-only brews and traditional craft beers made with hops. The pros found the CRISPR beer to be even hoppier than the traditional craft beer, citing notes of “Fruit Loops” and “orange blossom.”
“That was a really surprising and fun finding,” said Denby.
RELATED: CRISPR Could Domesticate Wild Crops While Avoiding 'Frankenfoods'
Denby’s startup, Berkeley Brewing Science, is busy developing more flavor combinations that can be engineered into common brewer’s yeast. But Denby acknowledges that consumers who are already wary of genetically modified foods might be hesitant to embrace a bioengineered beverage.
“In most brewing processes, you can actually purify the yeast out of the beer, so the yeast is a processing agent as opposed to an ingredient,” said Denby. “The end product doesn’t have any genetically modified material in it.”
Denby also points to studies showing that Millennials who understand biotechnology are more willing than the general population to purchase GM foods and beverages.
Maybe they just need to call it Save the Planet IPA.