Brave New Yeast

It’s hard to imagine a world without yeast. Most of us ingest it daily in our bread, beer, and wine as people have done for thousands of years. Ancient Mesopotamians and Sumerians were making beer and bread as early as 10,000 BC. A study of wine jars from the tombs of ancient Egypt determined that yeast had been used in winemaking at least as far back as 3150 BC.

The useful little microorganism called Saccharomyces cerevisia is invisible to the naked eye, but it can become airborne, travel great distances, and get onto skin and clothing. And the spores are very hardy. Case in point: as an avid sourdough lover, I still make my own bread from a sourdough culture passed on to me by my father-in-law in 1965. When a niece from Holland visited me in the ’90s, she wanted to learn to bake sourdough bread. She asked if she could take a portion of the wild yeast culture with her. I took some sourdough starter, spread it on a plate, and set it outside in the sun to dry. I then pulverized it and sealed it in a Ziplock bag. A few weeks later, after rehydrating and feeding flour to the dried yeast culture, my niece baked sourdough bread in Amsterdam.

Over centuries, people have learned how to culture specific strains of yeast. One of the most consistent problems for brewers and winemakers is keeping the yeast strain they’re using pure and uncontaminated by other strains and wild (airborne) yeast. Most brewers, winemakers, and bakers use yeast cultured by laboratories under carefully controlled conditions. Today, many different strains are available for different fermentation processes. Bakers, brewers, and winemakers want the perfect strain for their own needs, especially if it speeds up the fermentation process and eliminates “off” flavors. To feed those desires, scientists are creating genetically modified yeasts, which might be just about the worst idea that I can imagine. Consider that yeast travels through the air like pollen, which means that GM yeast could find its way into brews and bread just like non-GM yeast does.

Yeast is literally everywhere. It belongs to the Phylum Ascomycota, the largest division of fungi. The same group includes delectable morels and truffles, as well as the fungus responsible for the dreaded Dutch Elm disease. These organisms differ from plants in that they lack chlorophyll, and so they cannot photosynthesize. To reproduce, they must feed on other organisms. Without them, decomposition could not take place. Dead and spent matter would accumulate.

In bread baking, yeast feeds on the flour, producing carbon dioxide bubbles that push up the dough. In brewing, the spores feed on the barley sugars and release alcohol and carbon dioxide. Similarly yeast feeds on grape sugars to make wine. In each case the reaction—fermentation, the conversion of sugars to alcohol and carbon dioxide—is the same:

C6H12O6( (Glucose) + Saccharomyces cerevisia =
2C2H5OH (Ethanol) + 2CO2 (Carbon dioxide)

People have been satisfied with how this process has worked for at least 12,000 years. Though anyone can brew ales, ferment wines, and make bread, it takes careful study, patience, and experience to make the finest of these products—in fact, it is an art.

Over 20 years ago, the first research on the genetic engineering of brewing yeasts began, and genetically engineered strains have been developed. One of these GE yeasts allows the brewing of “lite” beer, which has a lower alcohol content. Even though these GE yeasts are available, it seems breweries are not using them—or if they are, they aren’t telling anyone. According to Cornell University Cooperative Extension, US processors are not currently using GE yeast in beer and bread.

As owners of an organic brewery, we must show our certifiers proof that we are not using genetically engineered yeast, along with an affidavit from our yeast supplier that the yeast is free from GMOs.

But it’s a different story for winemakers. The wine industry is booming. Wine grapes are now grown in every one of the lower 48 states, and wineries are springing up everywhere. It comes as no surprise that scientists have genetically engineered wine yeast. In fact, Saccharomyces cerevisiae strain ML01 is now commercially available and approved for use by the FDA in the United States. Springer Oenologie (a division of Lesaffre Yeast Corporation) has released the first GM wine yeast to the North American market.

Why genetically engineer wine yeast? In wine-making there are two fermentations: the alcoholic and malolactic, in two separate reactions. Natural wine yeast only accomplishes the alcoholic fermentation. The genetic engineers have created a Saccharomyces cerevisiae strain that will conduct malolactic fermentation as well, which eliminates the need for additions of another distinct microorganism, lactic acid bacteria. No one knows what the long-term risks to wild yeast and other yeasts are, or the health implications of this GE yeast.

Genetics Professor Emeritus Joe Cummings, from the University of Western Ontario, writes in Sustainable Agriculture, “The United States Food and Drug Administration in 2003 designated the genetically engineered yeast Saccharomyces cerevisae strain ML01 to be a substance generally recognized as safe&The GM wine yeast did not appear to have been tested for toxicity in animal feeding experiments nor was the must [the grape residue] and finished wine. The FDA review seemed to be based on faith rather than on science.”

The biotechnology industry claims that genetic engineering of products and processes is well regulated, and our government oversees thorough testing to prove safety. However, the British medical journal, The Lancet, points out that international faith in the FDA is fast eroding because approvals are frequently influenced by political pressure. Certainly the approval of GE wine yeast leaves fundamental—and extremely unsettling—questions to be answered.

Because the US has no labeling requirements for GE products, we don’t know which companies are using GE yeast. I’ve spoken to winemakers in Mendocino County who were outraged to learn that GE wine yeast had been approved and is now out in the world. We learned during the Measure H campaign that at least 30 field trials with GE wine grapes had been conducted in California, according to officials at UC Davis. We know that trials are being conducted with GE yeast. It would behoove the wine industry to find out where these trials are being conducted. In the meantime, the best way to stop this nonsense is to boycott wines and all other products whose producers cannot prove they don’t use GMOs.

In the meantime, my bread is rising in the kitchen. I wonder if any GE yeast has drifted into the dough.

Els Cooperrider spearheaded Measure H, the first GMO ban in the nation. A botanist, Cooperrider worked in medical research for 24 years before becoming co-owner of the country’s only organic brewpub.

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