A team of US scientists said Thursday they have taken an important step toward engineering painkillers from yeast, a process that has raised both hope and concern worldwide.

The report in the US journal Science describes how researchers at Stanford University genetically engineered yeast to convert sugar into hydrocodone — an opioid in the same chemical family as morphine — in just three to five days.

However, it would take a huge amount a yeast to make just one dose of painkiller, the researchers added.

Typically, it take more than a year to produce a batch of medicine from poppy plants, which are harvested, processed and shipped to pharmaceutical factories so that the active drug molecules can be extracted and refined.

The engineered yeast was made with a combination of “plant, bacterial, and rodent genes to turn sugar into thebaine, the key opiate precursor to morphine and other powerful painkilling drugs,” said the report.

“The molecules we produced and the techniques we developed show that it is possible to make important medicines from scratch using only yeast,” said senior author Christina Smolke, an associate professor of bioengineering at Stanford.

“If responsibly developed, we can make and fairly provide medicines to all who need.”

Other researchers have made a series of advances using yeast over the past year, in what an accompanying report in Science magazine called “a race to install the complex opioid pathway in yeast.”

The report went on to describe the Stanford team’s advance as “one of the most elaborate feats of synthetic biology to date.”

Jens Nielsen, a synthetic biologist at Chalmers University of Technology in Goteborg, Sweden — who was not involved in the research — called it as a “major milestone.”

Some experts have raised concern about technology that could facilitate home-brewed heroin and other painkillers.

Prescription opioids are addictive and already cause thousands of overdose deaths in the United States each year.

Others say such technology could make it easier to get painkillers to those in need who do not have access to them around the globe.

The World Health Organization estimates that 5.5 billion people have little or no access to pain medications.

Still, the prospect of home-brewed heroin is quite a ways off.

Smolke’s team said they went only so far as to demonstrate a proof of principle, and that it would take 4,400 gallons of bioengineered yeast to make a single dose of painkiller, according to a university statement.