Modified yeast boosts vitamin A in bread

JOHNS HOPKINS (US) — A genetically modified yeast that bakes a critical nutrient right into bread has the potential to help combat malnutrition in impoverished areas.

A team of undergraduates at Johns Hopkins University using synthetic biology techniques enhanced common yeast so that it yields beta carotene, the orange substance that gives carrots their color. When it’s eaten, beta-carotene turns into vitamin A, a nutrient that prevents blindness and death in children.


Team member Arjun Khakhar, a junior biomedical engineering major, grew up in Bombay, India, where he saw widespread poverty and malnutrition.

“The major problem in developing countries right now is not that people are hungry and starving because they don’t have enough food,” he says. “What people don’t have now is the [right type of] food that they need to survive. Vital nutrients like vitamins are just missing from their diets, because they can’t afford fruits and vegetables. That’s what we wanted to provide through VitaYeast.”

Arjun and his teammates—who were preparing for iGEM, the International Genetically Engineered Machine competition—came up with the idea of an enhanced starter dough that can be shared easily and cheaply among large groups of impoverished people. The bread baked from this dough could avert health problems that occur when vitamins and other nutrients are missing from their diets.

Build a better yeast

Yeast, which helps make bread rise, does not normally produce vitamins. To make it happen, the students, from a variety of science and engineering majors, had to genetically tweak the single-cell microbes. The team members figured out how to add to yeast cells certain DNA sequences that triggered a series of biochemical reactions producing beta carotene. They are now working on yeast that also produces vitamin C, another crucial nutrient needed in impoverished areas.

Jef Boeke, a leading yeast expert and a professor of molecular biology and genetics, is one of the VitaYeast team’s faculty advisers.

“One of the great things about iGEM teams, which are mostly made up of undergraduates, is that those students, frankly, will not believe that something is impossible,” Boeke says. “If you tell them that something is impossible, they will go off and do it. I find that to be very exciting.”

Working in lab space provided by Boeke and other faculty members, the students solved the science challenges and produced samples of their enhanced dough. But would VitaYeast yield bread that looks and smells good enough to eat?

To find out, the students bought a bread-making machine, found a simple recipe online and turned their lab into a makeshift kitchen.

“We wanted to simulate the process that a regular person might go through to bake bread,” says team member Steffi Liu, a junior biomedical engineering major from Edison, N.J. “The only thing that’s different in the recipe is that we substituted our vitamin A yeast for the normal dry packaged yeast.”

Lab turned bakery

The resulting bread, she says, “looks exactly the same as normal bread. Definitely the same smell! The lab smelled amazing after we baked the bread. Everybody wanted a bite of it. But obviously we can’t do that.”

Because the lab bread contains a genetically engineered ingredient that has not undergone safety testing or received approval from government regulators, the students are not permitted to eat it. But they are encouraged by the tempting aroma and traditional texture and appearance.

In recent years, some genetically engineered foods have been rejected by malnourished people merely because they did not look, smell, or taste like the familiar food staples. The Johns Hopkins students are banking on greater success, partly because they are thinking small.

“VitaYeast is a tiny component; it gets killed in the bread,” says Noah Young, a senior biomedical engineering major. “We’re not genetically modifying the wheat. We’re not genetically modifying the flour or the water. We’re genetically modifying something like 1 percent of the bread recipe. When you bake VitaYeast bread and you look at it, it looks like normal bread.”

The VitaYeast project has qualified for this year’s iGEM finals Nov. 5-7 at the Massachusetts Institute of Technology. In the annual iGEM contest, students from around the world present projects based on synthetic biology, a burgeoning field in which researchers manipulate small bits of DNA and other biological material to make cells carry out new tasks.

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