The discovery is good news for millions of people who need medical treatment that relies on human proteins - including haemophiliacs, cancer patients and sufferers of various genetic diseases.
The scientists hope the technology can be used to create human proteins in large quantities and make it possible to use as drug proteins that they cannot yet mass-produce.
Useful proteins include insulin, blood factors that treat haemophilia, proteins used to boost the blood cells of cancer patients as well as multiple sclerosis drugs.
Experimental proteins are in the works that could also treat cancer and help patients with genetic diseases including cystic fibrosis.
In theory, any disease that has a faulty gene as its basis could be treated with a therapeutic protein.
Cheaper, faster, safer
Tillman Gerngross, associate professor of biochemical engineering at Dartmouth College, said on Thursday the discovery was a major breakthrough.
"This technology has the potential to revolutionise the way therapeutic proteins are made - better, cheaper, faster, safer - and offer a level of control over the quality of the end product that has never existed before," said Gerngross, who helped lead the study.
"This technology has the potential to revolutionise the way therapeutic proteins are made"
professor of biochemical engineering, Dartmouth College
Gerngross is also chief scientific officer at GlycoFi, a private company in Lebanon, New Hampshire, which he helped set up to develop and exploit the technology.
Some human proteins, such as insulin, can be made cheaply now using bacteria. The bacteria are simply genetically engineered to make the protein.
But this process only works with some proteins, Gerngross said.
Most human proteins are covered with complex sugar
molecules. But therapeutic proteins with sugars attached to them are hard and costly to make, and carry certain health risks.
Human protein machine
Writing in the journal Science, Gerngross and his colleagues said they added five human genes to the yeast Pichia pastoris, making it into a human protein machine.
"We've essentially been able to humanise the yeast," he said. "The process time is shorter and yield much, much higher."
It may be possible to make existing products more cheaply and Gerngross said his company may be able to patent the process and make the equivalent of a cheaper generic version of an expensive protein-based treatment.
Gerngross believes his technology is more precise and safer than cell-based methods.
The process will also challenge the fledgling industry of bio-engineered animals. Goats, sheep, rabbits and cows have all been genetically engineered to make human proteins in their milk.