Munich Scientists Tinker with Yeast

Zymology by | Jan 2013 | Issue #72

Photo by Astrid Eckert/TUM

A group of young scientists in Germany have managed to brew a beer with added flavors that doesn’t break the Bavarian Reinheitsgebot, the 1516 purity law that stipulates beer must only contain barley, hops and water (yeast would have been included too, had 16th-century scientists known microorganisms existed). By tinkering with the genes in yeast, students at the Technical University of Munich have engineered the microorganisms to impart additional flavors and substances to their beers, like lemon and caffeine.

“We think we found a loophole,” says Fabian Froehlich, a graduate student at TUM. Froehlich and his team of microbiologists thought to engineer ale yeast (Saccharomyces cerevisiae) while brainstorming in early 2012. The idea came from just outside their window: Their laboratory is steps away from Weiheinstephan, the oldest brewery in the world.

Modifying yeast’s genetic makeup is simpler than you’d think. Much like adding a gene to corn to make it more resistant to drought, the German scientists inserted different genes into different strains of ale yeast to manufacture substances like caffeine during fermentation. Because the scientists are essentially plugging in a new snippet of code into the yeast’s genetic instructions, it’s no surprise that some biologists call it hacking.

Brewers know they can achieve clove and banana aromas by brewing with Hefeweizen ale yeast, or impart spicy and fruity characteristics using a Belgian Trappist yeast. But like heirloom tomatoes or a purebred Boston Terrier, these properties have been selected for and perfected over generations. The German students are simply speeding up the evolutionary process by inserting genes already known to produce certain flavors and additives. They’ve managed to brew a lemon beer, a caffeine beer and a sweet licorice-like beer.

The lemon beer uses a modified yeast strain that produces limonene, a compound normally used to add lemon flavors to food and drinks. The licorice beer has thaumatin, a compound that conveys a licorice-like sweetness that they predict would bode well in a Porter. Their caffeine beer has caffeine-producing yeast, though the dosing has varied from batch to batch. The team also attempted an anti-cancer beer brewed with yeast that produces xanthohumol, a chemical derived from hops that has been shown to inhibit tumor development and inflammation in mice, but they were unsuccessful.

The team got together in February 2012 to brainstorm a project with which they could enter an international biotechnology competition called iGEM (the international genetically engineered machine competition). iGEM is an annual synthetic biology competition that pits teams of students from around the world against each another to engineer a living organism using interchangeable genetic pieces called BioBricks—think of LEGO blocks that can be moved around and used to code different biological functions. Past projects have included pigmented bacteria, biological sensors that change when they find arsenic, and wintergreen or banana-smelling bacteria. With their modified yeast project, the Munich team placed in the top 16 out of 190 teams last October.

“The TU Munich project suggests that there is a great deal we could do using brewer’s yeast,” says Rob Carlson, a frequent judge at iGEM and author of Biology is Technology: The Promise, Peril, and New Business of Engineering Life. “I am, of course, all for making more interesting beer. But I think the project also points the way to making all sorts of interesting compounds in relatively simple fermentation systems.”

That’s the whole idea behind the iGEM competition: creating biological parts and developing laboratory techniques that can be applied across industries to manufacture things like biofuels, vaccines and beer.

As for selling their beer, the students admit the German brewing industry and beer market are very conservative. In fact, the idea of genetically modified food and drink is a major turn-off throughout Europe. They think they might have a better chance marketing their brews in the States. And has the team tasted its brews? Yes. Are they any good? “I think we need to practice our homebrewing,” admits team member Simon Heinze. “But the limonene was very intense. When we opened the flask it really smelled like beer and lemonade.”