NATURE By Elie Dolgin
The feat, described on 27 February in Nature, turns a sugar in brewer’s yeast (Saccharomyces cerevisiae) called galactose into tetrahydrocannabinol (THC), the main psychoactive compound in cannabis (Cannabis sativa). The altered yeast can also produce cannabidiol (CBD), another major cannabinoid that’s attracted attention lately for its potential therapeutic benefits, including its anti-anxiety and pain-relief effects.
To build their cannabinoid factory in yeast, synthetic biologist Jay Keasling at the University of California, Berkeley, and his colleagues modified several genes found in S. cerevisiae, and introduced others from five types of bacteria and from the Cannabis plant. In total, they needed to make 16 genetic modifications to transform galactose into inactive forms of THC or CBD. Heating the cannabinoids switches them into their active forms. The team produced roughly 8 milligrams per litre of THC and lower levels of CBD.
But those yields would need to increase by at least 100-fold for the cost to be competitive with plant-extracted cannabinoids, says Jason Poulos, chief executive of Librede, a company in Carlsbad, California, that holds the first patent on a process for making cannabinoids from sugars in yeast.