Hoppy Beer Without the Hops

University of California, Berkeley (UC Berkeley) biologists have engineered strains of brewer's yeast that not only ferment the beer, but also provide two of the prominent flavor notes provided by hops. Yeast is preferred instead of hops because growing hops uses lots of water, not to mention fertilizer and energy to transport the crop, all of which could be avoided by using yeast to make a hop-forward brew. A pint of craft beer can require 50 pints of water merely to grow the hops.

The engineered yeast strains were modified using the gene editing tool CRISPR-Cas9. Charles Denby and Rachel Li from UC Berkeley inserted four new genes plus the promoters that regulate the genes into industrial brewer's yeast. Two of the genes – linalool synthase and geraniol synthase – code for enzymes that produce flavor components common to many plants. In this instance, the genes came from mint and basil, respectively. The two other genes were from yeast and boosted the production of precursor molecules needed to make linalool and geraniol, the hoppy flavor components.

The researchers used a specially designed software program to get the right mix of promoters to produce linalool and geraniol in proportions similar to the proportions in commercial beers produced by Sierra Nevada Brewing Company. They then asked Charles Bamforth, a malting and brewing authority at UC Davis, to brew a beer from three of the most promising strains, using hops only in the initial stage of brewing to get the bitterness without the hoppy flavor. Hop flavor was supplied only by the new yeast strains. In double-blind taste tests, employees of Lagunitas Brewing Company in Petaluma, California, characterized beer made from the engineered strains as more hoppy than a control beer made with regular yeast and Cascade hops.

For more details, read the Berkeley News.