A revolutionary discovery for the production of beer 27.03.2018

For many beer drinkers, bitter taste and distinctive hop aroma are the most important attributes of their favorite drink. But hops are very expensive, consuming 100 billion liters of water annually in the United States alone.

To get around these problems, scientists have figured out how to brew "hoppy" beer without the use of... hops.

Bioengineers have created a genetically modified yeast that synthesizes the aromatic components of hops - the terpene alcohols geraniol and linalool. In the process of making beer with this yeast, hops can be omitted, which significantly reduces the cost and simplifies the production process. Double-blind testing of an experimental batch of the drink showed that such a beer has an even more pronounced taste and aroma than an American ale brewed in the traditional way.

Hops give the beer its characteristic bitterness and aroma. To achieve the desired taste, hops are added to the wort during the brewing process, and to give aroma - at later stages of the preparation of the drink; this procedure is called beer hopping. There are many varieties of hops that differ in the concentration of aromatic components. However, even within the same variety there can be variation in essential oil content, and this is one of the reasons why beer characteristics can be difficult to standardize.

The aroma fraction of hops contains many components, but researchers have found that two molecules from the class of terpenes - geraniol and linalool - make the main contribution to the hopping of beer, at least for varieties popular among American brewers. These substances are formed from a single precursor with the participation of two different synthase enzymes.

Bioengineers from the University of California and the Bioenergy Institute at Emeryville (USA), in collaboration with the California brewing company Lagunitas, have developed a technology that allows beer to be hopped without the use of hops. To do this, the genes for enzymes for the synthesis of geraniol and linalool were inserted into the genome of an industrial yeast strain used in brewing. In addition, researchers have learned to regulate the expression of these genes in order to purposefully change the taste of beer.

Since the enzymes involved in the synthesis of these terpenes have not yet been identified directly in hops, the scientists tested several linalool and geraniol synthase genes from other aromatic plants. It turned out that a shortened version of the enzyme from mint and a full-length enzyme from basil showed a sufficient level of activity in yeast cells for these two substances. In order to enable the synthesis of the terpene precursor, the bioengineers also had to overexpress several of the yeast's own enzymes. To integrate the genetic cassettes into yeast DNA, the researchers used the CRISPR-Cas9 system.

To test the new technology in practice, the authors of the work prepared a small experimental batch of beer with each of the strains without the use of hops. Control "traditional" batches used Cascade hops from five different American farms. Comparisons of beers have shown that the use of hops from different locations results in variation in terpene concentrations, and thus flavor variation. At the same time, the use of modified yeast gave a more stable result.

In the final experiment, the researchers prepared an American ale according to a classic recipe using "dry hopping" technology, when hops are added to the beer already at the fermentation stage, or with genetically modified yeast. Tasters in double-blind testing did not notice a significant difference between the presence or absence of "dry hopping", but the experimental beer, brewed with modified yeast, clearly had a hoppy aroma.