“Hacked” yeast used to brew THC and other cannabis compounds.

Nature has some, uh, heady science in the form of brewer’s yeast genetically modified to produce chemicals usually found in marijuana – the healthy ones *and* the fun ones:

The feat1, 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.

The hope is that this fermentation process will enable manufacturers to produce THC, CBD and rare cannabinoids that are found in trace amounts in nature more cheaply, efficiently and reliably than conventional plant-based cultivation.

Previous work described constructing parts of the cannabinoid production line in yeast, but not the complete process. The latest study is the first that has “put it all together and shown that it actually works inside one cell, which is cool”, says Kevin Chen, chief executive of Hyasynth Bio in Montreal, Canada, one of at least ten companies working to produce cannabinoids in engineered yeast, bacteria or algae.

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 cannnabis 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.

Scientists at Demetrix, a company formed by Keasling in 2015 to work on this problem, have already boosted the cannabinoid yield of this process by several orders of magnitude, says Jeff Ubersax, chief executive of the firm in Emeryville, California.