Researchers from Stanford University have genetically engineered yeast to make painkilling medicines, a breakthrough that heralds a faster and potentially less expensive way to produce many different types of plant-based medicines.
For thousands of years, people have used yeast to ferment wine, brew beer and leaven bread.
Now, the engineers describe how they reprogrammed the genetic machinery of baker's yeast so that these fast-growing cells could convert sugar into hydrocodone (a form of opioid) in just three to five days.
"This is only the beginning. 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," said senior author Christina Smolke, associate professor of bio-engineering.
Hydrocodone and its chemical relatives such as morphine and oxycodone are opioids, members of a family of painkilling drugs sourced from the opium poppy.
It can take more than a year to produce a batch of medicine, starting from the farms in Australia, Europe and elsewhere that are licensed to grow opium poppies.
Plant material must then be harvested, processed and shipped to pharmaceutical factories, where the active drug molecules are extracted and refined into medicines.
Though the output is small - it would take 4,400 gallons of bioengineered yeast to produce a single dose of pain relief - the experiment proves that bioengineered yeast can make complex plant-based medicines.
An important predecessor to this work has been the use of genetically-engineered yeast to produce the anti-malarial drug artemisinin.
The artemisinin experiments proved that yeast biosynthesis was possible, but involved adding only six genes.
The Stanford team had to engineer 23 genes into yeast to create their cellular assembly line for opioids.
"This is the most complicated chemical synthesis ever engineered in yeast," Smolke noted in a paper appeared in the journal Science.
The authors, however, acknowledged that the new process to make opioid painkillers could increase concerns about the potential for opioid abuse.
"We need options to help ensure that the bio-based production of medicinal compounds is developed in the most responsible way," they added.
