A commercial brewery is really a factory. Raw ingredients like grain and water go in one end, flow through pipes and tanks, and beer comes out the other side. But you could gut and replace all those pipes and tanks, switch from one grain supplier to another, swap out the walls and the controllers, and the same beer would still flow from the taps, metaphorically speaking.


The following is excerpted from Proof: The Science of Booze, by Adam Rogers.


The one thing the brewery cannot afford to lose is a finicky microbe that is the not-so-secret power behind the whole show. If you are a brewer and you plan to make a product people like, and keep making it the same way, you must maintain your yeast. The same goes for wineries, and even for distilleries — before you can distill a spirit, you have to have something fermented to start with. If you lose your yeast, you're dead.

In fact, "We're dead" is exactly what went through Rebecca Adams's mind when she arrived at work one day in late November . Head of the lab at Jennings Brewery in England's Lake District, Adams had slogged her way to work after a massive flood — sixteen inches of rain in twenty-four hours that pushed the Rivers Cocker and Derwent over their banks and put the stone walls, arched bridges, and whitewashed buildings of the medieval town of Cockermouth, at the confluence of the two, under ten feet of water. When Adams got to Jennings, she saw that they'd lost most of their service machinery—the boiler, the air compressors, the chillers. But that wasn't the worst part. Jennings makes real ale, an endangered species of drink made almost nowhere else in the world. Technically, real ale requires a specific variety of yeast that, during fermentation, floats on top of the sugary wort instead of sinking to the bottom. Ale is a rich, big-bodied, chewy experience very different from German-originated lager- and pilsner-type beers. For the British, ale is a cultural touchstone. The yeast is one of the things that make ale special. At Jennings after the flood, the yeast was gone. Drowned.

"I was there by half past six together with most of the operators," Adams says, "and we honestly didn't know whether we'd be working again." They could replace the machines. The yeast was a whole other kind of problem.

The miracle of yeast is awesome enough to strain credulity. It's a fungus, a naturally occurring nanotechnological machine that converts sugar to the alcohol we drink. It breeds pretty much everywhere and is one of the organisms on which scientists have built much of our knowledge of how life works . . . and, postscript, it also makes possible the baking of bread. Unbelievably practical and staggeringly improbable — yeast is practically science fictional. When Douglas Adams invented an equally useful biotechnology, the language-translating Babel fish, in his Hitchhiker's Guide to the Galaxy, he included an aside that said it was so fantastic that it disproved the existence of God (because it would imply the existence of a benevolent Creator, and proof belies faith, but without faith there can be no God. Poof! God "vanishes in a puff of logic"). And yet: here's yeast. Eats sugar, makes ethanol.


I'm not saying yeasts are divine . . . but exactly years before Douglas Adams published his book, Ben Franklin told essentially the same joke, only more succinctly. Franklin said that rain falling on grapes, which could then be turned to wine, was "a constant proof that God loves us, and loves to see us happy." Granted, Franklin didn't know he was talking about yeast, because nobody knew what yeast was until about 150 years ago. Yet we humans became dependent on it, without even knowing it was there. In utter ignorance, we made yeast into our partner. Absent knowledge of the mechanisms that made yeast work, the stuff was a miracle — the provenance of people who might as well have been wizards. Divining its secrets, figuring out that a living creature invisible to the naked eye was an agent of transformation, sparked a scientific revolution.

Yeast lives as a single-celled organism that is neither plant nor animal, neither bacteria nor virus. The fungus family includes every mushroom you've ever seen, lichens, rusts and smuts, athlete's foot and the Candida that infects people's most intimate parts, Dutch elm disease, the parasite that causes dandruff, and slime mold, the single largest creature on earth. Like animals, fungi tuck their genetic material — their DNA — into a structure inside their cells called a nucleus. Like plants, fungi have walls around their cells that provide strength and protection. In plants, that wall is mostly cellulose and lignin — the hard-to-break stuff you probably know better as "wood." Fungi mix in a little chitin, which is almost identical to cellulose save for the addition of nitrogen—and it's the main ingredient in insect exoskeletons and octopus beaks. Nature, weird in tooth and claw.


Yeast was the first eukaryote—that is, the first creature with cells and nuclei—to have its genome sequenced. That was in ; biologists were in a rush to see what its DNA looked like because in a way yeasts are the fundamental unit of cell biology. Yeasts grow quickly and easily in a lab, but because they have nuclei just like we do, they are an excellent model system for life like us. They are the critter that has taught us much of what we know about the cellular world, makng them, as one article puts it, "famous and atypical . . . an excellent model for the basic features of eukaryotes and for experimentation, but a poor model for other fungi."

All that, and they ferment. Assuming that combustion—fire—is ￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼civilization's most important chemical reaction, then yeast are responsible for the chemistry in the number-two slot.


After the flood in Cockermouth, Jennings Brewery started to clean up. The company bought new equipment, but the most important thing the brewers needed was in a steel tank full of liquid nitrogen, waiting for just such an emergency in a four-story building in the town of Norwich, miles to the southwest. That's the National Collection of Yeast Cultures, a research lab with a side business in preserving copies of yeast strains used by British brewers — offsite backups kept in case of something like, oh, let's say, a massive flood.

In February of 2010, Jennings reopened with all-new service equipment—most of it relocated to higher floors in case of another flood. But for Rebecca Adams, it was the return of the yeast that signaled the true reopening of the brewery. "Once we were working again, they sent a five-barrel tank of our yeast back up to us, which was an exciting day," she says. "It felt like we were going to have a future again."


To read more about the yeast vault that saved Jennings, check out Proof.

The above is excerpted from PROOF: The Science of Booze, © 2014 by Adam Rogers. Reproduced by permission of Houghton Mifflin Harcourt. All rights reserved.




Adam Rogers is the articles editor at Wired, where his feature story "The Angels' Share" won the 2011 AAAS Kavli Science Journalism Award. Before Wired, he was a Knight Science Journalism Fellow at MIT and a writer covering science and technology for Newsweek. He lives in Berkeley, California.

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