A new study published in the journal Nature describe a method to genetically alter yeast to produce cannabinoids, the active compounds in cannabis, including the psychoactive ingredient tetrahydrocannabinol (THC), as well as the non-psychoactive cannabidiol (CBD).
Typically, yeast produces ethanol through the fermentation process when exposed to sugar. However, the new strain of yeast developed by scientists at the University of California Berkeley produces cannabinoid compounds. The principal investigator of the study, Jay Keasling, professor of chemical and biomolecular engineering at the University of California Berkeley, said the process is akin to brewing beer. “You feed the yeast sugar and they produce the cannabinoid you want to produce, rather than ethanol, which they would normally produce,” he said.
The scientists inserted specific genes into the yeast’s DNA, including copies of genes used by the cannabis plant to synthesize cannabinoid molecules. The new genes regulate the production of specialized enzymes, which catalyze reactions to metabolize sugar into cannabigerolic acid, a precursor of cannabinoid molecules, which in turn is catalyzed into production of THC and CBD.
The process of genetically engineering yeast to make it produce different molecules is not new, with genetically modified yeast strains already producing insulin and even a new type of morphine-like painkiller.
Cannabinoids are naturally-occurring active compounds found in cannabis and hemp. So far, over 113 different cannabinoids have been identified in the cannabis plant. Recently, cannabinoids have attracted a lot of attention due to their medicinal properties and potential health benefits. Both CBD and THC are currently being examined in several clinical trials as potential treatment options for conditions such as anxiety, chronic pain and epilepsy. Currently in Canada, CBD can be prescribed to treat pain associated with multiple sclerosis with the pharmaceutical Sativex.
Cannabinoids typically occur in small quantities in cannabis and hemp plants, and mass-producing them in yeast could help the processes of drug development and medical research. Since yeast can be grown in large tanks, and does not require large quantities of energy, including electricity, water and fertilizer in order to grow.
Therefore, using yeast to produce cannabinoids could potentially serve as an environmentally-friendly alternative to harnessing them from plant sources. In addition, yeast mature faster than cannabis, expediting the production of cannabinoids.
In addition to CBD and THC, the team of researchers was also able to produce other rare cannabinoids, as well as some cannabinoids which do not occur in nature, opening the possibility of new medical applications.