Yeast, used by humanity for millennia to make wine, beer and bread, may have a new use, say researchers who've genetically engineered a strain of yeast to create powerful painkilling medicines.

Baker's yeast has been genetically reprogrammed to act on sugar, converting it to pain-killing hydrocodone in just three to five days, researchers at Stanford University report.

In addition to a faster method, it could provide a potentially less costly way to produce a number of different types of medicines normally created from plant sources such as the opium poppy, they say.

Opiods, a class of drug including hydrocodone and its chemical cousins oxycodone and morphine, can require more than a year to produce from poppies grown on licensed farms around the world, which must by harvested, processed and then shipped to pharmaceutical factories around the world.

That suggests any method of speeding up the process could be valuable, the researchers say, although the challenges are considerable.

"When we started work a decade ago, many experts thought it would be impossible to engineer yeast to replace the entire farm-to-factory process," says senior study author Christina Smolke, a Stanford associate professor of bioengineering.

The output of their experiments has been miniscule — 4,400 gallons of the bioengineered yeast yielded a single dose of painkilling drugs — but as a proof-of-concept effort, it is considered a success, Smolke says.

"This is only the beginning," she says. "The techniques we developed and demonstrate for opioid pain relievers can be adapted to produce many plant-derived compounds to fight cancers, infectious diseases and chronic conditions such as high blood pressure and arthritis."

The process involved introducing DNA into yeast cells that instructs them to create a chemical assembly line, the output of which is the desired medicine, Smolke explains.

Some of the 23 genes involved in the genetic engineering effort come from yeast, while others are from plants, bacteria and even rats.

In the same general way that yeast can work on sugar and turn it into alcohol, the engineered yeast can take sugar, break it down and reassemble it into an opioid drug, the researchers say.

Concerns that the technology might someday allow the illicit production of drugs like heroin are unfounded, Smolke says, at least as it currently stands.

"It's definitely the case that no one could take these strains now and use them for commercial production, or abuse them for nefarious purposes," Smolke says. "You could get more of these compounds from eating a poppy seed bagel. You really could."