Biologists at The University of California, Berkeley (UC Berkeley) have discovered a new way to produce the flavours and aromas of hoppy beers without using hops.

The researchers formulated strains of brewer’s yeast that can be used to ferment the beer and provide two of the prominent flavour notes provided by hops.

Employees of California’s Lagunitas Brewing Company, who underwent double-blind taste tests of UC Berkley’s beer, noted the product made from the engineered strains were more hoppy than a control beer made with regular yeast and Cascade hops.

Lagunitas innovations manager Bryan Donaldson detected notes of ‘Fruit Loops’ and ‘orange blossom’ with no off flavours.

The engineered yeast strains were changed using CRISPR-Cas9, a gene-editing tool invented at UC Berkeley. The researchers inserted four new genes and the promoters that regulate the genes into industrial brewer’s yeast.

“Growing hops uses lots of water, which could be avoided by using yeast to make a hop-forward brew.”

Two of the inserted genes were linalool synthase and geraniol synthase, which the researchers took from mint and basil. These are the codes for enzymes which produce flavour components common to many plants. The other two came from yeast and increased the production of precursor molecules needed to activate the linalool and geraniol.

Charles Denby, one of two primary authors of the UC Berkeley paper appearing this week in the journal Nature Communications, noted that growing hops uses lots of water, which could be avoided by using yeast to make a hop-forward brew. It is reported that a pint of craft beer needs 50 pints of water to grow the hops.

Denby and Li have launched a start-up named Berkeley Brewing Science and they intend to use this start-up to market UC Berkeley’s hoppy yeasts to brewers.

They also plan to produce other strains that include plant flavours not usually in beer from the canonical ingredients of water, barley, hops and yeast.