Heineken brewing facility in Amsterdam.

The sun is glaring overhead. I am dripping with sweat and eyeing a taco stand across the street as I wait for my beer in the tasting room of White Labs. This whole ordeal is a bit strange because White Labs is not really known for their beer, despite an international reputation in the brewing industry. The company specializes in yeast — the small creatures that carry out fermentation to create delicious foods, from bread to beer and wine — but they also consult with brewing companies on quality control. They supply yeast strains to beer manufacturers and make small batches of their own beers at their headquarters in San Diego.

India Pale Ales (IPAs) make my world go ‘round, so I order the flight deck, which comes with four different varieties. Surprisingly, each of them is identical, from the heating to the hops and everything in between — the only difference is the strain of yeast used during fermentation. Every sip that I take is a unique experience, highlighting the range of flavors that yeast give off during the brewing process. One of the IPAs tastes fruity, like raspberries, while the cloudy beer beside it tastes rich and bitter.

A flight of beers, each with a different color and taste.

All of these different brewing yeast strains come from White Labs’ signature product, called the Yeast Bank, which is a collection of different yeast strains that large-scale beer manufacturers and homebrewers can purchase. Each strain of yeast is used to brew a different style of beer, from ales to lagers and even kombucha. The founder and CEO of the company, Dr. Chris White, started White Labs after developing a library of yeast strains as part of his PhD at the University of California, San Diego. During the last 20+ years, White Labs has dramatically expanded the Yeast Bank. All of their strains are derived from species found in nature and are non-GMO.

It is important to clarify some terms before I delve in to how each of these unique yeast strains can manage to create such distinct beers. There are a lot of beer styles, including stouts, porter, pilsner, pale ale, mild ale, IPA and Hefeweizen. One of the definitive books on beer styles, called The Taste of Beer: A Guide to Appreciating the Great Beers of the World by Roger Protz, is a good place to start if you are keen to learn more. Certain regions of the world are known for producing distinct styles of beer; a good example of this would be the famous German What Beers or American Porters.

The process of brewing (good) beer, which has been around for at least 5000 years (uncovered at Godin Tepe in the Zagros Mountains of Iran), is complex and takes years to master; you can read about the basic steps here.

Pottery from Gobin Tepe. Image from the Oriental Institute Museum, Chicago.

There are two main types of yeast used during the fermentation process, called top-fermenters (Saccharomyces cerevisiae, ales, stouts, porters, wheat beer) and bottom-fermenters (Saccharomyces carlsbergenesis, lagers).

Some of the intriguing strains offered by White Labs include:

WLP099 Super High Gravity Ale Yeast — A strain of yeast that can ferment up to 25% alcohol, which is probably a higher ABV than any beer you have ever tasted. As beers become higher ABV, they begin to lose the taste of actual beer and begin tasting like other types of alcohol. This strain achieves a very high alcohol fermentation because it possesses genes that can break down dextrins, a specific class of sugars, and convert them into alcohol.

WLP002 English Ale Yeast — A strain of yeast from England that has a very high rate of flocculation. These yeast clump together into clusters of hundreds of thousands of cells and drop to the bottom of the beer after fermentation, resulting in clear beer. Other yeast strains which are not high flocculants will often stay in the liquid, making the drink cloudy.

Pinnacle Distillers Yeast — One of the most interesting strains that I encountered; this yeast has one of the highest fermentation temperatures (92–9⁸⁰F) and thrives in acid environments (pH 3.5–6.0). Most importantly, it can produce ethanol up to 16% weight/volume.

Kombucha Co-culture — Kombucha is a beverage made from the fermentation of sweet tea. Basically, a yeast:bacteria co-culture is added to sweetened white or green tea and fermented. The yeast produce ethanol while the bacteria produce acetate, giving the kombucha a vinegar-y taste. Fermentation takes anywhere from a week to a month and the end-product only contains about 0.5–3.0% ABV.

Kombucha, made from sweet tea and a co-culture of yeast and bacteria, originates from the Chinese Qin dynasty.

Synthetic, genetically-engineered strains not offered by commercial distributors are even more exciting:

Synthetic Yeast Strain created by Jay Keasling’s lab at UC-Berkeley — One of the bigger beer-related news items in 2018 was the creation of a novel, synthetic yeast strain that biosynthesizes aromatic terpenes, the small chemicals that gives beer its distinct, hoppy flavour…without the use of hops. The study, led by Charles Denby, created yeast that could effectively replace the use of hops in brewing beer. Hops have nearly doubled in price in recent years and require tremendous amounts of water to grow. Every year, about 100 billion liters of water are required for the irrigation of hops in the U.S. alone. A panel of expert beer judges drank the beer made from this synthetic yeast strain and compared it to beers made using the traditional process of hops and yeast, and determined that the beer made from the synthetic strain tasted as hoppy or hoppier than other varieties.

You can read the full study in Nature Communications here.

Brewer’s Yeast that Produce Different Terpenes to Add Flavors — An active area of research in synthetic biology is the rational engineering of yeast so that, during the fermentation process, terpenes are produced in addition to ethanol. Terpenes are the chemicals that give beer their unique flavors — they can taste like raspberries, oranges, lemons or thousands of other aromatic substances.

Different terpenes, typically found in plants and fruits, produce distinct flavors and aromas. Image from www.naturesmedicines.com.

Beer that Glows Green — Probably one of the dumber things that I have seen, but a novelty nonetheless. A group of biohackers engineered Brewer’s Yeast (Saccharomyces cerevisiae) with a sequence of DNA encoding Green Fluorescent Protein, or GFP. During the fermentation process, GFP is produced and the resulting beer glows bright green. It adds absolutely no flavor and I do not think I would want to drink something that looks radioactive (even though it is safe).

Yeast colonies on an agar plate that express GFP and glow green.

Yeast distributors like White Labs in San Diego provide a valuable product for the $111.4 billion dollar beer industry — from homebrewers and commercial distributors alike — using only natural, non-GMO strains. But the field of synthetic biology is quickly developing yeast strains that can be used to brew beers that are more environmentally-friendly and, potentially, tastier than traditional strains.