Beer is America’s favorite alcohol, with 42% of drinkers stating that they prefer beer to wine (34%)1. In its oldest form, beer can be traced back multiple millennia and in its many variations have been popular throughout recorded history. The beers most of us are familiar with today likely contain the following ingredients: water, malt, hops and yeast. Beer is created by first making wort, a sweet starch water made by mixing hot water and a starch source such as malted barley. Wort is then boiled down to concentrate its sugars and hops are added to imbue the liquid with bitterness, flavors, and aromas. Yeast is finally added to the hopped wort for fermentation where it converts sugars into ethanol and carbon dioxide.
As a society we have become more environmentally conscious. This has led us to think about the impact of our personal choices on the world at large, including our beverage choices. A recent study out of the University of Michigan found that the upstream emissions of beer in the state of Oregon were equal to 202,700 metric tons of carbon dioxide, which is comparable to running 42,800 passenger vehicles for a year2. The largest contributors were packaging, refrigeration, and raw material production. Within raw material production malted barley production required the most energy, with hops contributing very little. This review utilizes a study conducted by the Climate Conservancy that specifically studied the life cycle assessment of New Belgium’s Fat Tire Amber Ale. However, this amber ale is not a “hoppy” beer and requires 20 times less hops than common craft brews3. Hop-forward beers have become so popular that the demand for hoppy IPAs has increased 10 times in craft beer industry in the past 10 years4, making the question of sustainable hop production an important topic. Hop production for brewing is energy intensive. Emissions come from use of agricultural machinery, irrigation, fertilizer use and associated nitrous oxide release, and kilning. In addition to the environmental impact of hop production, the changing climate poses a threat to hop production. Germany and the US are the world’s largest hop producers contributing to 2/3 of global production. In recent years droughts have caused reduced yields and altered compositions of hops in both Europe and the Pacific Northwest region of US6, where most domestic hop production occurs.
One strategy that provides a novel solution to this problem is use of genetically modified yeast that can impart a hoppy flavor to beer without the addition of hops through the addition of terpenes. Terpenes are a class of aromatic compounds that contribute to the aroma and flavor of plants, vegetables, and flowers, including hops. Two monoterpenes, linalool and geraniol, have been identified as key molecules responsible for hoppy-ness. Researchers at UC Berkely’s Keasling lab led by then graduate student Charles Denby were successful in identifying yeast-active linalool and geraniol synthases and engineering brewer’s yeast strains that expressed them, thereby creating yeast strains that were capable of imparting the flavor and aroma of hops7.
Berkeley Yeast, the company founded by Dr. Denby, sells and custom makes yeast strains for beer and wine production. Several breweries have brought these beers to market. Drake’s Brewing founded in San Leandro, California has utilized the High Sierra yeast strain, which contain terpene producing genes, in two of their now retired beers. Weird Science, a pale ale, and Steroid Era, a brut IPA, both feature Berkeley Yeast’s genetically modified yeast strain8, 9. Lallemand Brewing, one of the largest distributors of brewing yeast, have also created a new genetically engineered yeast strain called Sourvisiae®10. This strain features the addition of the lactate dehydrogenase gene which allows brewers to simultaneously ferment and sour beer instead of the traditional two-step process required to create sours. Rhinegeist, a Cincinnati based brewery, uses the Sourvisiae® for all of its sour beers11.
In addition to adding genes, genetic engineering of yeast has allowed brewers to fine tune production through removal of unwanted characteristics such as off flavors or dry mouthfeel. Normally during the fermentation step brewer’s yeast converts fermentable sugars such as glucose, fructose, maltose, and maltotriose into ethanol and carbon dioxide. This process leaves behind non-fermentable complex carbohydrates (starch and dextrins). However, brewer’s yeast strains that contain the STA-1 gene, which encodes a glucoamylase enzyme, can break down these complex carbohydrates into fermentable sugars. These yeast strains are termed diastatic and are able to continue fermentation beyond what is desirable, or even after packaging. Starches and dextrins contribute to the body of beer. Over-fermented beer from diastatic strain contamination have a drier mouthfeel, clove-like off flavor, and carry the risk of post-packaging explosions12.
Saccharomyces trois, a yeast strain known for producing tropical notes such as mango and pineapple in its finished product, contains this STA-1 gene. Berkeley Yeast have created a new yeast strain using genetic engineering that has all of the characteristics of its parent strain Saccharomyces trois, except for the STA-1 gene13. Thus allowing brewers to take advantage of the positive characteristics without the drawbacks of using a diastatic strain. Fieldwork Brewing has utilized this non-diastatic strain for their fruity double IPA Loser’s Club Vol. VII14.
As with most technological innovations that threaten the status quo, there has been push back from brewers who prefer the traditional methodology. Brewers such as Matthew Brynildson from Firestone Walker Brewing Co. worry that using genetically engineered yeast strains would open up doors to a future where beer can be made “with water, a drum of the cheapest sugar source you can find, and yeast that makes all the flavors that we used to get from barley and hops”15. Others find that these innovations will allow brewers to be more creative, sustainable, and produce beer that suffers less from batch-to-batch variability. Regardless of where brewers stand on the use of GMO yeast, the changing climate and consumer demand for a more sustainable future are likely to dictate the future of beer production.
1. Dugan A. Americans Still Favor Beer Over Other Alcoholic Beverages. https://news.gallup.com/poll/238100/americans-favor-beer-alcoholic-beverages.aspx
2. Heller M. Food Product Environmental Footprint Literature Summary: Beer. State of Oregon Department of Environmental Quality. https://www.oregon.gov/deq/FilterDocs/PEF-Beer-FullReport.pdf
3. Shellhammer DGHaTH. An Overview of Sustainability Challenges in Beer Production, and the Carbon Footprint of Hops Production. 2019;doi:10.1094/TQ-56–4–0731–01
4. Shellhammer SRLaTH. How Hoppy Beer Production Has Redefined Hop Quality and a Discussion of Agricultural and Processing Strategies to Promote It. 2019;doi:10.1094/TQ-56–1–0221–01
5. Potopová V, Lhotka O, Možný M, Musiolková M. Vulnerability of hop-yields due to compound drought and heat events over European key-hop regions. International Journal of Climatology. 2021;41(S1):E2136-E2158. doi:https://doi.org/10.1002/joc.6836
6. Kennedy C. Climate & Beer. National Oceanic and Atmospheric Administration. https://www.climate.gov/news-features/climate-and/climate-beer
7. Denby CM, Li RA, Vu VT, et al. Industrial brewing yeast engineered for the production of primary flavor determinants in hopped beer. Nature communications. Mar 20 2018;9(1):965. doi:10.1038/s41467–018–03293-x
8. Weird Science. Drake Brewing. https://drinkdrakes.com/beers/weird-science/
9. Steroid Era. Drake Brewing. https://drinkdrakes.com/beers/steroid-era/
10. Sourvisiae. Lallemand Brewing. https://www.lallemandbrewing.com/en/united-states/product-details/sourvisiae/
11. Garrett J. Yeast of Eden — Why Genetically Modified Yeast Could Be the Next Step in Beer’s Evolution. https://www.goodbeerhunting.com/blog/2020/1/13/yeast-of-eden-why-gmo-yeast-could-be-the-next-step-in-beers-evolution
12. Krogerus K, Gibson B. A re-evaluation of diastatic Saccharomyces cerevisiae strains and their role in brewing. Applied microbiology and biotechnology. May 2020;104(9):3745–3756. doi:10.1007/s00253–020–10531–0
13. Alexandre Trois. Berkeley Yeast. https://berkeleyyeast.com/beerstrains/p/alexandretrois
14. Loser’s Club Vol. VII. Fieldwork Brewing. https://fieldworkbrewing.com/beer/losers-club-vol-vii/
15. Bland A. GMO Yeast Mimics Flavors Of Hops, But Will Craft Brewers Bite? https://www.npr.org/sections/thesalt/2018/04/04/599147983/gmo-yeast-mimics-flavors-of-hops-but-will-craft-brewers-bite
Written by Kana Hamada, Associate for Helikon Consulting