A Very Versatile Hungry Fungus

Dating back millions of years, the story of yeast is the story of innovation in not only science, but taste.

It was around the time when quarantine was getting old that I began to understand why so many loaves of bread were popping up on social media. I had even witnessed a “loaf-off” amongst my 18-year-old brother’s friends. The COVID-19 pandemic has led bored teenage boys to compete over Snapchat for the best home-grown sourdough starter. Home-grown starters may be the only option now, for grocery delivery services and grocery stores have seen yeast run quickly out of stock. The alternative, growing a home starter, requires flour, which also is hard to come by. This has left home-baking-hopefuls out of luck, even in the UK. BBC producer Andrew Chiles. “I thought I was the only clever dick clever enough to bake his own bread,” he said in an opinion for The Guardian in March. “I have flour now, but nowhere, anywhere can I get yeast. Where has it all gone? There must be so much out there that if a biblical flood were added to our woes, all this unused yeast would dissolve in it and rise up, frothing, to bake us in a giant crusty loaf of calamity.”

Chiles was a little off the mark about how baking works, but he is not alone in his sentiments. Yeast is in high demand, not only for home bakers, but for home-brewers, and even for distillers. Yeast is a remarkably multifaceted microorganism. It is used to make the alcohol in take-home cocktail kits sold out of bars during the pandemic, but it can also be used to make the hand-sanitizer.

Rodd Seher works in the lab for Lallemand Yeast in Montreal. He said, “I know in the distilled spirits business, a lot of their distilleries are actually making hand sanitizer now.” Lallemand Yeast is one of 17 major yeast production companies that the economic research institute IMARC, called the “competitive players” in the yeast industry. Seher said Lallemand is “actually either donating or selling their yeast at cost to those distilleries as long as those distilleries are donating or selling their hand sanitizer to where it’s needed.” Distillers, in turn, are reported to have been giving away their free hand sanitizer, such as Glass Distillery in Washington, and Old Fourth Distillery in Georgia.

In laboratories around the world, Lallemand works with yeast in a multiplicity of industries: brewing, oeneology (wine), baking, biofuel, distilled spirits, bio-ingredients, plant care, animal nutrition, and pharmaceuticals, just to name a few.

How is this possible? Yes, the yeast we are talking about is the same stuff as the flakey, golden-yellow seasoning or the little yellow packets in the baking aisle at grocery stores, and also the same stuff in that bubbling cauldron in your beer-nerd neighbor’s back yard. But Andrew Chiles needn’t worry about a tidal wave combining with this yeast to turn us into a giant loaf of bread. Even without shelter in place orders, yeast are, quite literally, everywhere.

Yeast are hungry fungi that live and thrive off naturally-occurring sugars. Humans take advantage of yeast’s impressive metabolism by feeding it flour for bread, grain for beer, fruit for wine, etc. In a process called fermentation, yeast feast on the sugars in these foods, converting them into products that include carbon dioxide gas and liquid ethanol alcohol. In bread, the carbon dioxide expands gluten proteins to create the air pockets you see in sourdough or ciabatta. In fermented beverages, the gas causes sparkly carbonation, and the ethanol supplies the alcoholic flavor that ever-so-slightly clenches the tonsils, warms the throat, and slightly numbs the roof of your mouth.

During fermentation, producers can manipulate yeast for desired results. In beer, for example, yeast can be largely credited with the vast diversity of flavors, according to Seher. “Yeast is crucial because you can create a lot of good flavors, but it can also create a lot of bad flavors, too,” Seher said. “It's up to the talents, basically a mix of artistry and science by the brewer to actually provide the appropriate conditions to the yeast so that does produce good flavors and not bad ones.”

These conditions can include water temperatures, the presence of certain characteristics in the yeast, or the amount of yeast used. Brewers need to know the traits of their strain of yeast in order to get what they want from yeast. Imperial Yeast, a brewer’s yeast company based in Portland, Oregon, displays some of the traits for each strain of yeast sold on their website. The words like “flocculation”, and “attenuation”, according to the company’s owner Owen Lingely, reference characteristics of how each strain of yeast responds to the fermentation process.

“We have 200 strains in our bank; we say there’s 35 strains on the website,” Lingely said. “All those strains have been selected over the years to produce certain types of flavors.”

Humans’ ability to select yeast and manipulate it has resulted in some creative endeavors. Erik Fowler, the education manager for the the brewer’s yeast company WhiteLabs inc. in California, described one project that produced beer useing yeast found in the beard of a brewer, and how another used yeast that had been living in Norwegian farm houses for decades. Fossil Fuels Brewing Co., whose motto is “Here’s to beer, to science, and the marriage of the two,”,

brews with yeast extracted from the gut of a 45-million-year-old bee preserved in its hardened tree sap grave.

Yeast and science have had a long and happy marriage. The most common kind of yeast used by humans, Saccharomyces Cerevisiae, has evolved nearly in tandem with humans. In his book “The Yeasts: A Taxonomic Study”, Cletus Kurtzman accounts a long history of scientific discoveries about and using yeast. From ancient Egyptian drawings of the world’s first bakeries, to crucial mid-19th century discoveries in biochemistry and cell biology, to the first sequencing of a eukaryotic (meaning the cells contain a nucleus bound by a membrane) genome in 1996, this species of yeast seems to pop up everywhere. “The domestication of Saccharomyces Cerevisiae can be considered a pivotal event in human history,” Kurtzman wrote. “It is a model organism”.

According to Kurtzman, in 2011, the global annual production of Saccharomyces Cerevisiae was 1 million tons. Markets and Markets, an independent research group, estimated the yeast industry to be valued at over $3.5 million in 2017, with a projected growth rate of 9 percent annually until 2022. Markets and Markets attributes the growth to the flourishing baking industry, increased consumption of fermented beverages, and a heightened demand for bioethanol.

Bioethanol is an industrial fuel alternative, produced using the same process that distillers use to make spirits or hand sanitizer: distillation. This is when the liquid product of fermentation is vaporized, then trapped and re-concentrated so all that is left is liquid ethanol. Erik Fowler of WhiteLabs calls this process “quick and dirty” because distillers don’t bother manipulating the yeast for flavor. Yeast are instead selected to create the most ethanol before the alcohol-- which is toxic to yeast-- kills it. “Through distillation you actually separate those compounds out and

then capture what you want, discard what you don't,” Fowler said. “Whereas beer, you just let it let the yeast create what it creates and that's what you drink.”

Yeast also assists in the production of drugs. In 2019, a team at UC Berkeley used brewer’s yeast to produce THC and CBD—the main active ingredients found in marijuana. Jay Keasling, who led the project, said yeast is a cheaper and more environmentally friendly way of producing cannabinoids. “We take the genes out of the plant that are responsible for making THC and CBD and we transplant them into yeast,” Keasling said. “We use the native chemistry in yeast, plus this new chemistry that we get by putting in genes from the plant, and we coax yeast into diverting those chemicals rather than into CO2 and ethanol, into the product we want to make”. In 2013, using the same method, and some of the same metabolic pathway, Keasling produced a version of the chemical artemisinin, which is used in the leading anti-malarial drug treatment.

With their interests in a different mode of health, food bloggers are raving about nutritional yeast, or “nooch”, which is dried, deactivated yeast. Nooch is high in protein, low in calories, and contains B12, a vitamin usually only found in animal products. Nooch is often used as a cheese substitute in vegan recipes; one food writer for Vogue magazine dubbed the savory powder “nature’s Cheeto dust”. According to the Vogue article, chef Gerardo Gonzales uses nooch to top traditional Mexican dishes that he’s made vegan.

Hopeful bread-bakers don’t need to go find yeast-- if you offer it food, yeast find you. This is how home-grown starters are made: leave out a mixture of food, and “wild yeast” from the environment will gather to feed and grow.

Matthew Mejia, a college student in Los Angeles who has taken up baking during his COVID-19 shut-in, mixed water and all-purpose organic flour for his homegrown starter, and was able to produce his first homemade loaf of sourdough rye bread.

“I think one of the more interesting parts about the process is how precisely you must be in order to cultivate a healthy starter,” Mejia said. “You have to measure the amount of flour in grams as well as making sure the temperature of the water you mix it with is always at 85 degrees. The starter is like having a baby boy or something, you have to make sure to feed and take care of it and you cannot let it die!”

Mejia was inspired to try his hand at baking after being forced to return from his study abroad semester in Florence, Italy. While there, he said the diversity and texture of bread he encountered fascinated him. Making his own bread at home, Mejia was able to see how the spongy lightness of bread forms. “The pockets of holes the starter makes, they’re so fascinating,” he said. “You can really see how alive your starter is when you see the holes.”

Erik Fowler’s WhiteLabs owns a restaurant and pub in Asheville, North Carolina, where the chefs have been getting extra creative with baked goods using their yeast during the COVID- 19 shutdown. “The major difference is baking yeast has been developed for efficiency,” Fowler said. The yeast traditionally used for making bread may be simplified to be fast-acting, but stripped of the complexity that brewer’s look for. By using brewer’s yeast, the bakers are able to bring slightly altered tastes to the sourdough cinnamon roles, yeast-risen cookies, and take-home pizza doughs they are selling during the shutdown.

Those home bakers who managed to get their hands on instant yeast for their at-home baking endeavors can still learn the science of yeast and taste. Both White Labs and Lallemand Yeast’s Seibel Institute offer educational courses for those wanting to learn more about yeast. Though most of these courses are usually in person, some courses and webcasts are available online during the shutdown. Lallemand Yeast’s Seibel institute, where Rodd Seher works, is North America’s oldest brewing school, and they work with everyone from amateurs to “Master Brewers”. Seher said he is still often surprised at how little people in the industry know about yeast.

“It's interesting to hear them not know that it's a living organism doing all these different things for their beer,” he said.

While the boom in hobby baking may be new, the fungus is old, and for this microscopic organism, the world of possibilities is enormous.

Story by Mardy Harding, 2021 graduating senior.

Mardy is an International Studies major. Outside of school, she works for the Foghorn, rock climbs, swims, browses the chocolate section at grocery stores, and works at a taproom where she continues her education in yeast.

Art work by Elizabeth Oswalt, graduating senior.