While it is a few days late for LePrecon, the pub crawl through Hoboken celebrating St. Patrick’s day, an article in Nature Communications announced the development of a genetically modified yeast that not only ferments beer but replaces the hops.
Brewers' yeast, Saccharomyces cerevisiae, ferments grains into alcohol and the addition of hops to the brewing process imparts a somewhat bitter, “hoppy,” taste that is increasingly popular. Hops taste resides in essential oils created by the plant in variable amounts. And while hops add flavor, they also add cost. Hops can be expensive, the increasing advent of craft beers has strained hops resources, and in some instances, the smaller breweries are shut out from hop supplies by larger competitors. And hops can be environmentally expensive in drought-prone climates as the hops necessary for one pint of beer require 50 pints of water. So eliminating hops may confer some economic advantage. As to the environmental benefits, the same folks that will applaud the water savings may have “concerns” about the use of genetically modified yeast despoiling a “natural” product – so let's call that a draw. Oh yes, for the naturally “woke” amongst us, those essential oils imparting hops’ flavor are terpenes; compounds that some scientists say are bad for our environment, presumably as they finish their cold beer.
Now while genetics, the environment and farming result in varying hop flavors, two terpenes, Linalool, and Geraniol, are the primarily “flavor determinants” of Cascade hops, the most widely used hops in craft beer. Two genes, Linalool and Geraniol synthase from mint and basil and two additional genes from yeast that boosted production of the terpene’s precursors were inserted using CRISPR-Cas9 technology into brewers' yeast’s DNA. This yeast was then used to brew up some beer. Now to be fair, the GMO yeast was introduced after the initial stage in beer production, the creation of the wort.
For those not readily familiar with beer fermentation, the wort is the initial fermentation of yeast and grain. Hops are added on three occasions after the creation of this sweet wort; the first time they are added to impart that hoppy bitterness, the second and third time to impart hops flavor. The genetically modified yeast replaced hops in the final two stages.
After IRB approval (you have to love science), 40 dedicated employees of the Lagunitas Brewing Company (28 males and 12 females), ages 20 to 50 with 2 to 154 tasting episodes annually participated in the evaluation. They were provided 5 2-ounce pours consisting of 1 control, three various genetically modified yeast beers and one blind control and asked to rank the tastings on a 9 point scale. They determined “that the finished beers exhibited a range of hop flavor/aroma intensity” or as Bryan Donaldson, Lagunitas’s innovations manager found “notes of ‘Fruit Loops’ and ‘orange blossom’ with no off flavors.”
The paper’s authors came to UC Berkley to work on “sustainable transportation fuels” using a methodology that employed microbial created terpenes. The brewing project “found them” according to first author Charles Denby. He along with his partner and second author, Rachel Li, have founded the Berkley Brewing Science to monetize their work. While the public relations piece accompanying the article points out that the two principals were able to “drink their research project” we should not fail to appreciate the science behind their achievement. They created four new chromosomes (the number found in brewers yeast) by inserting four different genes and promoters in each set of chromosomes and scaling up their work from a test tube to a 40-liter fermenting kettle.
Let's lift a pint in their honor.
Source: Industrial brewing yeast engineered for the production of primary flavor determinants in hopped beer Nature Communications DOI: 10.1038/s41467-018-03293-x