Home-brewing could soon take on a more dangerous twist: Scientists have engineered brewer's yeast to synthesize opioids such as codeine and morphine from a common sugar, an international team reported on Monday.

"It is going to be possible to 'home-brew' opiates in the near future," Christopher Voight of the Massachusetts Institute of Technology, who was not involved in the research, told reporters.

The process described in Nature Chemical Biology is inefficient, requiring 300 litres of genetically engineered yeast to produce a single 30 milligram dose of morphine.

But with improvements that are well within reach, that dose could be obtained from "a glass of yeast culture grown with sugar on a windowsill," Voight said.

Yeast cells have been genetically modified to produce the yellow beet pigment betaxanthin, which UC Berkeley researchers used to quickly identify key enzymes in the production of benzylisoquinoline alkaloids (BIAs), the metabolites in the poppy plant that could lead to morphine, antibiotics and other pharmaceutical agents. (William DeLoache/UC Berkeley)

For centuries, morphine and other opioids have been the go-to drugs for pain relief. But their molecular structure is so complex, they are isolated or manufactured from compounds in plants, such as opium poppies. Chemists have never been able to produce them on a practical scale from off-the-shelf components.

Scientists, however, recently reported engineering yeast to carry out the second part of the 15-step opioid-producing reaction. What remained was just the hurdle of coaxing yeast to carry out the first part.

That is what scientists at the University of California, Berkeley, and Concordia University in Montreal have accomplished.

Crucial enzyme from sugar beets

The researchers, led by John Dueber at the University of California, Berkeley, isolated a crucial enzyme from sugar beets, mutated its gene to make it more productive, and slipped it into yeast.

They then added more foreign DNA and achieved their goal: the yeast carried out the first half of the reaction that produces opioids.

An Afghan farmer works on a poppy field collecting the green bulbs swollen with raw opium, the main ingredient in heroin. The molecular structure of opiates is so complex that chemists have never been able to produce them on a practical scale from off-the-shelf components. (Rahmat Gul/Associated Press)

Combined with the earlier recipe for the rest of the reaction, said Dueber, "it's now a matter of linking (the steps) together and scaling up the process."

Outside scientists agreed, and expressed alarm over that prospect.

Although additional DNA tweaks could produce yeast that synthesize cheaper, less addictive, and more effective pain-killers, the creation of morphine-making yeast could dramatically increase access to illegal opiates, which have caused a scourge of addiction in many communities.

The study, which the authors alerted colleagues to before publication, could make illegal drugs "easy to grow, conceal and distribute," with little more than a home-brew beer-making kit, policy analysts at MIT and the University of Alberta warned in an accompanying commentary.

The analysts called for policies to regulate engineered-yeast strains, such as confining them to licensed facilities.

But the cat may be out of the bag. With the recipe for opiate-producing yeast now public, Dueber said, "anyone trained in basic molecular biology could theoretically build it."