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Would You Drink Beer Made With GMO Yeast to Conserve Water?

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Charles Denby and his colleague, Rachel Li, prepare to pour their yeast samples into beer fermenters at the brewery at UC Davis.  (Sarah Craig/KQED)

If you are a beer drinker, it might surprise you to learn how much water goes into one pint of beer. About 11 gallons just for the hops alone.

But there’s a scientist named Charles Denby who wants to replace those hops with genetically engineered yeast. And he’s doing this because he wants to make beer more climate-friendly.

“I'm really interested in making an impact on the process,” says Denby, “and if that means that we can cut out trillions of liters of water that’s used on hop agriculture every year, that’s really the pie-in-the-sky goal for me.”

Denby wants to replace hops because the crop is vulnerable to climate change.

Most of the nation’s hops, and many of California’s hops, are grown in the Yakima Valley in the state of Washington. And that area is expected to have less water because of higher temperatures and intense drought.

The UC Davis brewery where Charles Denby brewed the first batch of his GMO yeast. (Sarah Craig)

The challenge for Denby is creating yeast that tastes hoppy enough. I met him at a brewery at UC Davis last summer to see his experiment in action.


The sound of heavy metal filled the room and steam hissed from silver machines. Denby yelled over the noise and explained that beer is made from water, barley, yeast and hops. But the four batches he was making that day wouldn’t include that last ingredient.

Instead of hops, he added his GMO yeast to three large fermenters. As a control, he added generic yeast that he didn't genetically modify to the fourth fermenter.

His yeast is made with the genes from mint and basil plants. He combined these genes with yeast DNA, then mixed them with yeast cells. He’s hoping this process will lead to some interesting flavors.

Before Denby started this research, he wasn't a big beer drinker. But after his friend gave him a home brewing kit a few years ago, he got into the science behind it. His interest in brewing, along with a Ph.D. in molecular and cellular biology, led him to make a discovery.

“I was literally sitting in the bathtub reading this book about brewing science and I got to the section about hops. And they actually spelled out exactly what the molecules were for the primary determinants for hoppy flavor,” says Denby. “And I looked at the molecules and was like, ‘Oh my God.’ ”

Right now, he says he’s the only scientist using GMO yeast to make beer. But getting that beer to market is tricky because GMOs carry some heavy baggage.

Companies like Monsanto have made GMO crops resistant to pesticides that kill weeds. But these pesticides lead to diversity loss and they also drift to nearby farms and kill non-GMO crops.

Bill Freese, a science policy analyst at the Center for Food Safety, says these weeds eventually develop a resistance to the pesticides, and so more toxic chemicals are needed. And the cycle continues.

Charles Denby pours one of his GMO yeast solutions into a fermenter at the UC Davis brewery. (Sarah Craig)

But Denby explains he isn’t in the business of making harmful chemicals.

“I'll have friends and family say, ‘Oh I don't eat anything GMO,’ and I have to be very patient and just explain what the potential benefits are,” he says.

But his research still involves risk. There’s the fear his GMO yeast could escape and alter yeast in the wild.

And then there is the regulation of GMO products. There are no mandatory rules that say GMO products must be safe to eat or drink. There’s only a voluntary process by which scientists test their GMO creations themselves and then ask the FDA if they approve the product as safe. 

But there is a caveat. If a company doesn't submit for FDA approval and places their GMO product on the market, they would most likely face liability issues. Denby made sure to submit his results last year and is waiting to hear from the FDA.

While Freese says there should be more regulation, scientific research conducted so far has not detected any significant hazards directly connected with the use of genetically engineered crops, according to a 10 year review.

Denby says the benefits of his research outweigh the harms. “My position on GMO products has definitely evolved. I'm very pro. Obviously, you want to make sure they don't have allergenic effects, but you can save a lot of resources,” he says.

In the meantime, Denby wants to make sure his beer actually tastes good.

He reached out to Sonoma County's Lagunitas Brewing Co., and they set up a companywide taste test.

Charles Denby fills out a questionnaire after tasting his beers for the first time in the Sensory Lab at the Lagunitas Brewing Co. (Sarah Craig)

Denby brought the samples he brewed at UC Davis to the Sensory Lab at the brewery. I watched as Bryan Donaldson, the lab's innovation manager, led Denby through the process.

First, Denby sat down in a private booth. Then, a blue light came on and a small door slid open. A woman on the other side handed him a tray with four samples of his beer -- three from his GMO yeast and the fourth from the control.

After the tasting, Denby pushed back his chair and breathed. They actually tasted good.

“I've been nervous all day, all week, and I feel like a pretty profound sense of relief,” said Denby. “I guess the next thing that I'm nervous about is, is it going to be [similarly] perceived by the general public or a group of expert tasters as well, or is it gonna be just in my mind?”

But before leaving the lab, expert taster Bryan weighed in on the samples.

“I got some fruit notes off a couple of them," he commented. "One was straight-up Fruit Loops and then one was kinda orangey, like orange blossoms.”

Denby talks about the flavors in his beer with Bryan Donaldson, the innovation manager at Lagunitas Brewing Co. (Sarah Craig)

We headed to the company’s bar to try some other beers, and Denby told me his next step would be getting brewing companies to bottle his beer.

A few months later, I caught up with Denby to see if he got the taste testing results back. He told me the results were quite positive: two of his beers were hoppy enough for the judges.


Then he told me he had some exciting news. He received a grant from the National Science Foundation. He's starting his own brewery science company and wants to experiment with new flavors -- like passion fruit, gooseberry or broom flower. He says that by using genetically engineered yeast instead of real hops, beer can taste like anything.

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