Without yeast, we would be miserable as a species. For thousands of years, baker’s yeast has provided us with leavened bread. I can’t even picture a world without beer or wine, which rely on yeast to convert sugar into alcohol.

Now, scientists are using yeast to do something even more unlikely: producing the cannabis chemicals CBD and THC. They’ve converted brewer’s yeast into cannabinoid factories by inserting genes from the cannabis plant into the microorganisms. It’s part of a bigger effort to dissect and reproduce marijuana’s various chemicals in order to better comprehend the plant’s full potential.

This is how the procedure works. Depending on which enzyme they contain, two distinct yeasts create THC or CBD. Both possess the cannabis genes that make CBGA, which is significant. “CBGA is this type of central cannabinoid that’s the mother of all the other cannabinoids,” explains Jay Keasling, a chemical engineer at UC Berkeley and coauthor of a new study outlining the process in Nature.

To manufacture THC, that yeast makes CBGA, which is subsequently converted to THCA by a yeast enzyme. The CBD yeast uses its own enzyme to convert the CBGA mother cannabinoid to CBDA. (I know, it’s alphabet soup, but bear with me.) Now you have THCA and CBDA, which when heated, transform into THC and CBD.

The final section is quite similar to what is going on with the cannabis plant. It’s doubtful that you’d get high if you ate raw cannabis because it’s primarily THCA. The conversion of THCA to THC occurs only when heat is applied. (However, as cannabis flower cures, minor levels of THCA change to THC.) Edibles work because producers utilise a process called decarboxylation to convert THCA to THC.

Working with the original plant is dirty and complex, which is why academics and cannabis corporations are interested in other methods of manufacturing cannabinoids. To begin with, growing the substance requires a significant amount of time, water, and energy (if done indoors). It’s also difficult to extract some cannabinoids from flower. If you’re solely looking for CBD, for example, your extract may be tainted with THC. This is especially important if you want to extract CBD for use as a medicine—been it’s proved to be quite successful in treating epilepsy, for example.

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Having a vat of yeast producing pure, non-psychoactive CBD promises to make production much easier. “Being able to make it without contaminating it with THC is a really valuable thing,” Keasling says. Especially since the FDA may want to speak with you if you mistakenly give a psychoactive chemical to a patient.

It’s also possible that cannabinoid-producing yeast will make it easier to research cannabis in the first place. We’re dealing with a plant that’s incredibly complex, with over 100 distinct cannabinoids identified so far. Some of these substances are more common than others; for example, modern cannabis strains are high in THC, as producers have bred strains to be increasingly intoxicating over time. A cannabinoid like tetrahydrocannabivarin, or THCV, on the other hand, is found in considerably lower concentrations. “Now that we have a handle on being able to construct these things in a pure and relatively straightforward fashion,” adds Keasling, “we can start to verify what their functions are.”

Engineered yeast has previously been used to combat scarcity in various ways. Researchers discovered that taxanes from Pacific yew tree bark can combat cancer in the 1960s. Except for the Pacific yew, which conservationists feared would become extinct if it fell into the hands of a greedy medical establishment. Researchers designed bacteria to help create the drug—deforestation-free, just like they did with the cannabinoid-producing yeast.


The main advantage of cannabis is their scalability. The notion is that producing large volumes of CBD in vats would be significantly more efficient than growing greenhouse after greenhouse of cannabis plants. (This isn’t to imply that some people won’t like their cannabis farmed the traditional way.) However, to make it as effective as possible, you’d need to use the greatest cannabinoid concentrations available. That instance, you would want to optimise your yeast so that it can produce a large amount of product.

“Can you keep manufacturing it extremely concentrated, or does it become toxic to the creatures you’re employing to make it, and therefore you’ve reached your limit?” enquires Jeff Raber, CEO of the Werc Shop, a lab that dissects the components of marijuana.

Regardless of production challenges, the beauty of this type of bioengineering is that it provides a powerful platform for researchers to investigate not only what each cannabinoid might be useful for—whether treating anxiety, inflammation, or epilepsy—but also how the plant’s many cannabinoids interact with one another. This is known as the entourage effect, and CBD, for example, appears to reduce THC’s high effects.

Researchers will be able to play with these cannabinoids in isolation and in combination without having to wade through hundreds of other substances found in pure flower if they specifically produce them in the lab. “At the end of the day, a molecule is a molecule,” Raber explains. Cannabinoids produced by yeast are identical to those produced by plants. “It allows for greater formulation flexibility, possibly greater utility, and it may eventually scale faster than plants.” These types of initiatives may appeal to regulators more than those that involve “fields upon fields of plant stuff.”

This isn’t limited to cannabinoids. Raber and other academics are attempting to rebuild the chemical profile of marijuana. Terpenes, for example, are what give cannabis its distinct aroma, although they’re found all over the plant kingdom: Although limonene is not abundant in cannabis, it is a common product of the citrus industry. Instead of going to the trouble of collecting little amounts of limonene from a cannabis plant, the idea is to extract it from lemons.

The ultimate goal is to be able to customise cannabis goods, such as tinctures, to the interests of individual customers. This would allow for a personalised CBD-to-THC ratio, as well as other cannabinoids and terpenes, which could play a role in the entourage effect. Linalool, for example, is a terpene that may have anti-anxiety properties.

Let us celebrate yeast, that miracle microorganism and producer of all things good, such as bread, liquor, and bioengineered cannabinoids, in the near future.

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