Synthetic biologists are turning yeast into microscopic chemical factories that manufacture cannabinoids found in the marijuana plant (Cannabis sativa). Unlike the typical fermentation process during which yeast converts sugar into alcohol, the process described in a published this week transforms galactose—the sugar found in brewer’s yeast—into THC and CBD, as well as other cannabinoids that don’t naturally occur in the plant.
Berkeley postdoc Xiaozhou Luo and grad student Michael Reiter, who led the project, initially set out to produce “the mother of all cannabinoids, CBGA (cannabigerolic acid),” according to reporting on the findings. To do this, they modified a number of genes found in galactose (Saccharomyces cerevisiae) and introduced other enzymes from bacteria of the cannabis plant to create a new product.
By inserting a dozen different “starter chemicals” in place of the naturally occurring fatty acids, the scientists were able to use these new chemical pathways to build synthetic compounds that may contain therapeutic properties. If proven effective, these compounds could be patented because they’re not found in nature.
The popularity of marijuana’s non-psychoactive agent CBD has infused therapeutic and cosmetic markets and has also been approved as a treatment for pain relief, anxiety, and childhood epilepsy. THC, or tetrahydrocannabinol, the psychoactive compound (now legal in 10 states and the District of Columbia) has been used in FDA-approved medicines for cancer and AIDS patients, and is being studied for treatments of Parkinson’s, depression, and chronic pain, among others. But extracting these cannabinoids from the buds of the plant is costly, energy-intensive, and often toxic, resulting in chemical byproducts that pollute watersheds.
Yeast offers a cheaper, high-quality, more environmentally sound option, UC Berkeley professor of chemical and biomolecular engineering and faculty scientist at Lawrence Berkeley National Laboratory. This isn’t Keasling’s first foray into harnessing the sugar-hungry microorganisms. He and his team have used yeast to produce the malaria-fighting drug, artemisinin, and to convert plant waste into biofuels.
Previous studies have partially constructed cannabinoids from yeast, but this study is the first to achieve a complete biosynthesis of the major compounds of Cannabis sativa. While the technology is not yet ready for the market and likely won’t be for another couple years, scientists at Demetrix Inc., a company Keasling formed to tackle this very issue, have already “.”
This means that the cost of synthetic THC and CBD could someday be competitive with conventional plant-based products. Another bonus: there would be no risk of psychoactive contamination of a non-psychoactive product—something CBD consumers often wonder about.
Cannabis contains hundreds of other potentially beneficial compounds that are difficult to study because they occur in such small quantities. Yeast-based fermentation may make the extraction and modification of these compounds not only easier and cheaper, but more reliable, too.
As these findings continue to bubble up, of microbiologist Jim Bowie and colleagues at the University of California, Los Angeles, who are working on converting sugar into CBD without the genetic modification of cells.