Saccharomyces cervisiae
The UC Berkeley researchers, led by synthetic biologist Jay Keasling, developed a genetically modified yeast from Saccharomyces cerevisiae to produce Tetrahydrocannabinol (THC) and Cannabidiol (CBD) molecules. The research was published in the scientific journal Nature February 27th, 2019. The yeast is commonly used in beer and wine making.

The production of cannabinoids from yeast could be a cheaper and easier way of producing the valuable molecules which are currently widely used for treatment of medical conditions and, in the case of THC, consumed for the psychoactive effects. Cannabis high in THC, usually referred to as marijuana, is legal for recreational adult - use in 10 states and 13 others have decriminalized its use. Cannabis high in CBD, typically obtained from very low THC Industrial hemp, and the CBD molecule itself, are legal in most states. Both molecules are shown to be effective in treating many conditions and diseases, including pain, cancer, glaucoma, seizures, and many others.

"Once you've engineered it, you can grow out more of it," explained Jay Keasling, who is a Berkeley professor and a co-author of the study. "The yeast is in our freezers and whenever we want to grow more, we take a sample, put it into sugar water with a few other nutrients. If you've got the right sugar in there, it will produce the cannabinoids."

Keasling has already formed a company, Dimetrix, and patented the yeast. He says he can create THC for less than $400 per kg and hopes the company can produce lower cost CBD and THC which is also cleaner and more pure than what is currently cultivated from cannabis. This could make it more affordable for patients and consumers.

From the Abstract:
We report the complete biosynthesis of the major cannabinoids cannabigerolic acid, Δ9-tetrahydrocannabinolic acid, cannabidiolic acid, Δ9-tetrahydrocannabivarinic acid and cannabidivarinic acid in Saccharomyces cerevisiae, from the simple sugar galactose...

Our work presents a platform for the production of natural and unnatural cannabinoids that will allow for more rigorous study of these compounds and could be used in the development of treatments for a variety of human health problems.
Yeast is already used to produce other drugs such as codeine and morphine, as well as insulin. The research team has already used the yeast to create an anti-malaria drug that has dramatically lowered it's cost.