Researchers map genes of craft beer;

SAN DIEGO — Troels Prahl, a brewer and microbiologist at the Southern California yeast distributor White Labs, sits at his company’s tasting room bar with four half-pints of beer. He describes each between thoughtful sips.
The first has a malty backbone and a crisp body of raspberry, rosemary and banana, he says; the second, a waft of white raisin and final bite of olive brine; the third flows thick and smooth like a classic English ale; and the fourth is perfumed with a dry and subtle blend of nutmeg and fresh straw.
The beers’ colors are as varied as their flavors, ranging from cloudy gold to clear amber. Yet with the single exception of the yeasts used to ferment them, Prahl explains, they are all the exact same brew.
After thousands of years of unwitting domestication, brewing yeasts — the microorganisms that ferment a brewer’s tepid slop of grain, water and hops into beer — are as diverse as the beer they make.
And now two research teams, from White Labs and a Belgian genetics laboratory, are mapping out their sprawling genealogy, creating the first genetic family tree for brewing yeasts and the beers they make.
The laboratories have sequenced the DNA of more than 240 strains of brewing yeasts from around the world. Alongside samples from breweries like Sierra Nevada, Duvel Moortgat and Stone, “we’ve thrown in a few wine, bakers, bio-ethanol and sake yeasts to compare,” said Kevin Verstrepen, director of the lab in Belgium.
By getting a line-by-line reading of the 12 million molecules that make up the DNA of each yeast, Verstrepen said, the researchers will be able not only to tell how closely related two yeasts are (is Sam Adams’ closer to Stone’s, or Sierra Nevada’s?) but to answer other important questions: which breweries started with the same strains of yeasts, how these organisms evolved over time and, of course, how all of it translates to taste.
“Yeasts can make over 500 flavor and aroma compounds,” said Chris White, the founder of White Labs, affecting a beer’s alcohol level, clarity and texture. But while brewing yeast is one of the best-studied organisms in molecular and cell biology, exactly how its genes translate to brewing properties is still poorly understood.
By comparing the DNA of hundreds of yeasts, along with information on how they act and brew differently, “we’ll have a unique window into the genetic code,” said Prahl, who is leading the experiment at White Labs. He is comparing each yeast’s sequencing information with brewing data on more than 2,000 batches of beer — including the four he was tasting.
The researchers in the Belgian lab — a joint venture of the Flanders Institute for Biotechnology and the University of Leuven, Belgium — have even bigger plans. “With this information, we’ll be able to select different properties in yeasts and breed them together to generate new ones,” Verstrepen said. “In a few years we might be drinking beers that are far different and more interesting than those that currently exist.”
For brewers today, there are few options for generating new yeasts. Simply breeding strains together rarely results in a usable brew — because most brewing yeasts are highly specialized, the results are often the genetic equivalent of combining a bicycle with in-line skates. Each serves the same purpose, but applying parts from one to the other yields little more than a mess.
And while the genetic tools already exist to create new yeasts artificially — by splicing genes from one to another — because of the long-standing stigma associated with genetically modified foods, there is no market for them.
“Right now we have a few hundred genetically modified yeast strains patiently waiting in our laboratory’s freezer,” said Jan Steensels, a microbiologist with the Belgian lab, “but most brewers and consumers don’t want anything to do with them.” The data from the genomic project could allow researchers to design and breed new brewing yeasts without resorting to genetic modification.
By knowing which genes to track, and using computers and robotics to speed the process, a researcher could mate two different yeast strains thousands of times until, by chance, they produced an offspring with the perfect combination of genetic characteristics. “So let’s say there’s a yeast that produces an amazing fruity aroma in beer, but can’t ferment past 3 percent alcohol,” said Chris Baugh, a microbiologist at Sierra Nevada Brewing Co. in Chico, Calif., who is not involved in the project. A scientist who understood the genetics, he continued, “could then breed it with a more alcohol-tolerant strain.”
Novel yeasts are unlikely to end up in the beer of brewing giants like Budweiser, which for decades had protected its flagship lager yeast under armed guard. “Where this is really going to take off is in the craft brewing scene,” Baugh said. The number of craft breweries and microbreweries has exploded in recent decades, to roughly 2,500 today from fewer than a dozen in 1980; they now account for 14 percent of beer sales nationwide.
“And there is a big push for something new and interesting all the time,” Baugh said.
Only within the last few years has a DNA-sequencing project of this scale been possible. The project to sequence the first human genome, completed in 2000, took nearly a decade and cost almost $3 billion; new technologies and laboratory equipment have rapidly lowered the cost and accelerated the process. Today, the researchers can sequence a single yeast, which is much less complex, in a matter of days, for only a few thousand dollars.
The technology is so inexpensive that the first 96 strains at White Labs were sequenced free of charge by the biotechnology company Illumina, to assess one of its new sequencing machines. Rather than cost, the experiment’s true hurdle lies in sorting through the huge trove of newly acquired genetic data, said Prahl, who has partnered with the bioinformatics company Synthetic Genomics to parse his project’s data set.
Many researchers believe that brewers will soon routinely sequence yeast strains. “This project strikes me as sort of an inevitable thing that one can do,” said Randy Schekman, a yeast geneticist at the University of California, Berkeley, who shared the 2013 Nobel Prize in Physiology or Medicine. With the falling costs and rising speed, he added, “the sequencing is almost trivial at this point.”
But Schekman sees this type of research as an important prod to an industry that has long been wary of genetic techniques.
“Until recently, the brewing industry has been remarkably resistant to using the techniques of genetics and molecular biology to improve their brewing strains,” Schekman said. “It’s long overdue that someone has actually delved into the molecular basis between the differences in brewing strains.”

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