The world's first test-tube hamburger has already been synthesized and cooked at a cost of more than $300,000. Now a pair of young bioengineers in Silicon Valley are trying to produce the first glass of artificial milk, without a cow and with the help of genetically engineered yeast.

Like the creators of in vitro burgers, the scientists behind yeast-culture dairy are concerned about animal welfare and agricultural sustainability—but also about creating a food that will find a mass market. (Read: "Test-Tube Meat: Have Your Pig and Eat It Too.")

Because their petri dish milk will mirror the formula of the real thing—the yeast cultures will be churning out real milk proteins—it will retain the taste and nutritional benefits of cow milk, says Perumal Gandhi, a co-founder of the synthetic dairy start-up Muufri (pronounced Moo-free) in San Francisco, California. That will distinguish it from soy- and almond-based alternatives.

"If we want the world to change its diet from a product that isn't sustainable to something that is, it has to be identical [to], or better than, the original product," Gandhi says. "The world will not switch from milk from a cow to the plant-based milks. But if our cow-less milk is identical and priced right, they just might."

The Hard Life of Cows

Gandhi and Muufri co-founder Ryan Pandya are both vegans who view the livestock industry's practices as inhumane. The cows in a modern dairy, they argue, live in crowded barns. Their horns are removed to keep them from injuring themselves or farmworkers, their tails are often docked so that workers won't get a feces-laden smack in the face, and they're given growth hormones and antibiotics.

What's more, the cows are artificially inseminated every year so they'll keep producing milk—and then, as soon as they give birth, their calves are taken away, to make the milk available for humans.

"Fundamentally, you're controlling the reproductive system of an animal. It's incredibly invasive," Pandya says. "A lot of people are motivated by the environmental factors, but imagine that happening to an animal. Really, if you consider yourself an environmentalist and then you consume dairy, it's all for naught."

The industry's environmental impact is also substantial. Dairy production is responsible for roughly 3 percent of global greenhouse gas emissions each year, according to the Food and Agriculture Organization of the United Nations, mostly because cows belch methane. And although dairy is already a more efficient way than meat of converting plant feed into animal protein, bioengineers can do even better than nature, Gandhi says.

"Making an entire cow to make just the milk is inefficient," he says. "You're giving it all this feed and water, and most of it goes towards growing legs, growing a head, growing a liver and lungs—just living."

In contrast, Muufri's system can be likened to "an out-of-body udder" that only churns out milk.

Let's Make Milk

Making milk, while complicated in its own way, is nonetheless much simpler than growing meat.

"If you look at all the components, less than 20 make milk milk—give it the taste, structure, color you expect when you drink milk," Pandya says.

Muufri will contain only those essential proteins, fats, minerals, and sugars. Pandya and Gandhi's plan is to insert DNA sequences from cattle into yeast cells, grow the cultures at a controlled temperature and the right concentrations, and harvest milk proteins after a few days. The process is extremely safe, says Gandhi: It's the same one used to manufacture insulin and other medicines.

Although the proteins in Muufri milk come from yeast, the fats come from vegetables and are tweaked at the molecular level to mirror the structure and flavor of milk fats. Minerals, like calcium and potassium, and sugars are purchased separately and added to the mix. Once the composition is fine-tuned, the ingredients emulse naturally into milk.

By controlling the ingredients, however, Pandya and Gandhi hope to make milk more healthful. The team is experimenting, for instance, with sugars other than lactose, which 65 percent of adults have trouble digesting. And it has engineered a more healthful, unsaturated fat that retains the distinct flavor of dairy. Reproducing that flavor is a prime goal for Gandhi and Pandya, who were not always vegan—and who say they miss the taste of cheese, butter, and ice cream.

The Dairy Race

Last month Muufri, which began lab trials in May, received two million dollars in seed money from Horizons Ventures, a Hong Kong-based investment firm (no relation to Horizon Farms organic milk) whose portfolio of "disruptive start-ups" includes Siri, Spotify, and Facebook. Muufri hopes to perfect its concoction by next spring and to deliver it to store shelves as early as 2017, says Gandhi. A carton of Muufri is projected to cost twice as much as a carton of cow's milk, at least initially.

Muufri is not the only team attempting to create cow-less dairy products. Impossible Foods, started by a former Stanford University professor, focuses on animal-free meat business, but it's working on cow-less American cheese to accompany its burgers. It has $75 million in financial backing. Another outfit, Real Vegan Cheese, is run on crowdsourced funding by volunteer bioengineers in Oakland, California.

Meanwhile, worldwide dairy consumption continues to grow every year. Will consumers go for milk that's made in a lab by genetically modified organisms (GMOs)? The proteins made by Muufri yeast will be indistinguishable from natural ones, Pandya says, and the yeast itself is harmless.

"People who are anti-GMO who have legitimate concerns usually worry about supercrops taking over the natural world," he says. "We've essentially crippled the yeast, so if it does go out in the world, it'll produce only milk proteins and die within hours."

Some dairy scientists are skeptical that artificial milk will ever supplant the natural stuff. The 20 or so components of Muufri barely scratch the surface of milk's complex chemistry, says Philip Tong, director of the Dairy Products Technology Center at Cal Poly in San Luis Obispo, California.

"We've been milking [cows] for seven or eight thousand years," Tong says. "I doubt biotechnology could fully reproduce what Mother Nature intended." (Watch: "I Didn't Know That: Milking a Cow.")