Scientists have brewed a hoppy-tasting beer-without the hops

Modesto Morganelli
Marzo 21, 2018

The goal of hops in the brewing process is to add bitterness during fermentation, and "hoppiness" after.

A GENETICALLY engineered yeast makes beer taste of hops - without any actual hops.

Bryan Donaldson, innovations manager at Lagunitas, detected notes of "fruit-loops" and "orange blossom" with no off flavors.

Biologists at the University of California Berkeley came up with a way to create the aromas and flavors associated with hops without actually using hops.

Hops are the flowers of the hop plant Humulus lupulus. And hops are expensive.

A former UC Berkeley postdoctoral fellow, Denby has launched a startup called Berkeley Brewing Science with Rachel Li, the second first author and a UC Berkeley doctoral candidate.

Synthesising hoppy flavours in beer, in other words, means significantly less water and fertiliser is needed to produce the flawless pint.

The team behind the new research employed CRISPR technology to make the new yeast strains. Denby and Li 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. After a lot of testing and trials, the team decided that the genes from mint and basil spliced into with yeast worked the best. Genes from other plants that were reported to have linalool synthase activity, such as olive and strawberry, were not as easy to work with.

The remaining two genes that were used boosted the creation of molecules that are needed produce linalool and geraniol - which are the components of hoppy flowers - and they came from yeast.

The various genetic components - the four yeast, basil and mint genes, promoters and the Cas9 gene - were put into the yeast by way of a tiny DNA plasmid that was the shape of a circle.

Once the genes were isolated, the DNA of brewer's yeast was modified to make the fungi produce the same oils.

After that, yeast fix enzymes incorporated the four new genes and promoters. Today, beer-making procedures do not need hops for preservation but only for flavor, noted the report.

Denby came to UC Berkeley to work on sustainable transportation fuels with Jay Keasling, a pioneer in the field of synthetic biology and a professor of chemical and biomolecular engineering. They said their technique could help the beer industry reduce its dependence on hops.

The method was made trickier by the fact that commercial brewer's yeast has four sets of chromosomes, unlike the strains used in research labs, which typically possess a single pair. They found out that they needed to add the same four genes plus promoters to each set of chromosomes to obtain a stable strain of yeast; if not, as the yeast propagated they lost the added genes.

In the end, they were able to drink their research project, and continue to do so at their startup as they ferment batches of beer to test new strains of yeast.

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