Researchers engineer yeast to manufacture complex medicine

Stanford University bioengineers have figured out a way to make noscapine, a non-narcotic cough suppressant that occurs naturally in opium poppies, in brewer's yeast.

The researchers inserted 25 foreign genes into the one-celled fungus to turn it into an efficient factory for producing the drug. Many of the inserted genes came from the poppy, but several came from other plants and even from rats. All those genes were recipes for enzymes: protein machines that, working together, can build complex substances from simple starting materials.

The researchers also modified some of the plant, rat and yeast genes, as well as the medium in which the yeast proliferates, to help everything work better together. The result was an 18,000-fold improvement in noscapine output, compared with what could be obtained by just inserting the plant and rat genes into yeast.

"This is a technology that's going to change the way we manufacture essential medicines," said Christina Smolke,PhD, professor of bioengineering.

An additional hundredfold improvement will be necessary for commercial viability, she said, but much of that can be achieved by substituting large-scale bioreactors for simple laboratory flasks.

A paper describing the research will be published online April 2 in the Proceedings of the National Academy of Sciences. Smolke is the senior author. Yanran Li,PhD, a former postdoctoral scholar who's now an assistant professor of chemical and environmental engineering at the University of California-Irvine, and postdoctoral scholar Sijin Li, PhD, share lead authorship.