Forget Growing Weed—Make Yeast Spit Out CBD and THC Instead
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We as a species would be miserable without yeast. Baker’s yeast has given us leavened bread for thousands of years. And I don’t even want to begin to imagine a world without beer and wine, which rely on yeast to convert sugar into alcohol.
Now researchers have turned to yeast to do something more improbable: manufacturing the cannabis compounds CBD and THC. By loading brewer’s yeast with genes from the cannabis plant, they’ve turned the miracle microbes into cannabinoid factories. It’s a clever scheme in a larger movement to methodically pick apart and recreate marijuana’s many compounds, to better understand the plant’s true potential.
The process goes like this. Two different yeasts produce either THC or CBD, depending on what kind of enzyme they carry. Importantly, both carry the cannabis genes that produce CBGA. “CBGA is this kind of central cannabinoid that’s the mother of all the other cannabinoids,” says UC Berkeley chemical engineer Jay Keasling, coauthor on a new paper in Nature detailing the technique.
To make THC, that yeast produces CBGA, which then turns into THCA thanks to the yeast’s particular enzyme. For the CBD yeast, its own particular enzyme turns the CBGA mother cannabinoid into CBDA. (Alphabet soup, I know, but stick with me.) Now you’ve got THCA and CBDA, which turn into THC and CBD with the application of heat.
The end bit is not dissimilar from what’s going on with the cannabis plant itself. If you were to eat raw cannabis, it’s unlikely you’d get high, because it’s mostly THCA. It’s only after you apply heat that THCA transforms into THC. (Though small amounts of THCA convert to THC over time as cannabis flower cures.) Edibles work because manufacturers first transform THCA into THC with a process called decarboxylation.
The reason researchers and cannabis companies are interested in alternative ways of producing cannabinoids is that working with the original plant is messy and complicated. First of all, growing the stuff takes a lot of time, water, and energy (if you’re cultivating indoors). Extracting certain cannabinoids from flower is also a hassle. If you’re only after CBD, for example, there’s a chance your extract could be contaminated with THC. This is of particular concern if you want to isolate CBD for use as a medicine—it’s been shown, for instance, to be remarkably effective in treating epilepsy.
Having a vat of yeast churning out pure, non-psychoactive CBD promises to massively simplify production. “Being able to produce that in a way that’s uncontaminated with THC is a pretty valuable thing,” says Keasling. Especially since the FDA might want to have a word with you if you accidentally dose patients with a psychoactive substance.
Cannabinoid-producing yeast may also make it easier to study cannabis in the first place. We’re talking about a wildly complicated plant here, with more than 100 different known cannabinoids so far. Some of these compounds are more prevalent than others—modern cannabis strains are packed with THC, because cultivators have bred strains to be ever more intoxicating over the years. But a cannabinoid like tetrahydrocannabivarin, or THCV, shows up in much lower amounts. “Now we’re going to have a handle on being able to produce these things in a pure way, and in a relatively simple way, that maybe we can start to test what their functions are,” says Keasling.
Engineered yeast have been used to tackle the scarcity problem in other ways before. In the 1960s, researchers discovered that the taxanes from Pacific yew tree bark can fight cancer. All well and good, except for the Pacific yew, which conservationists feared would go extinct in the hands of an eager medical establishment. But as with this cannabinoid-producing yeast, researchers engineered microbes to help make the drug—deforestation-free.
For cannabinoids, the key benefit is scale. The idea is that you could crank out vast amounts of CBD in vats far more easily than by planting greenhouse after greenhouse of cannabis plants. (Which is not to say some folks won’t still appreciate their cannabis grown the old fashioned way.) But to make it as efficient as possible, you’d need to work with the highest possible concentrations of cannabinoids. That is, you’d want optimize your yeast to churn out a whole lot of product.
“Can you keep making it highly concentrated, or does it become toxic to the organisms that you’re actually using to produce it, and therefore you have a limit?” asks Jeff Raber, CEO of the Werc Shop, a lab that’s picking apart the components of cannabis.
Regardless of production hurdles, the beauty of this kind of bioengineering is that it gives researchers a powerful platform to dig into not just what each cannabinoid might be useful for—whether treating anxiety or inflammation or epilepsy—but how the many cannabinoids in the plant might interact with one another. This is known as the entourage effect: CBD, for instance, seems to attenuate the psychoactive effects of THC.
By selectively churning out these cannabinoids in the lab, it’ll be easier for researchers to play with them in isolation and with each other, without having to wade through hundreds of other compounds you’d find in pure flower. “Ultimately, a molecule is a molecule,” says Raber. Indeed, cannabinoids made from yeast are the same cannabinoids the plant makes. “It gives flexibility in formulation, it gives broader utility perhaps, and it may eventually scale faster than plants. Regulators might feel a lot better about these types of approaches than those that are fields and fields and fields of plant material.”
And this doesn’t stop at cannabinoids. What Raber and other researchers are pursuing is essentially a reconstruction of cannabis’ chemical profile. Terpenes, for example, are what give weed its characteristic smell, yet you’ll find these across the plant kingdom: Limonene isn’t super abundant in cannabis, but it is an abundant product of the citrus industry. The idea is that instead of going through the grief of extracting small amounts of limonene from a cannabis plant, you can get it from lemons instead.
The eventual goal is to be able to tailor cannabis products, such as tinctures, to a consumer’s preferences. This would allow for a customized ratio of CBD to THC, and eventually other cannabinoids and terpenes, which themselves may play a role in the entourage effect. The terpene linalool, for example, may have anti-anxiety effects.
In the nearer term, let us celebrate yeast, that miracle microbe and creator of all things good: bread, booze, and bioengineered cannabinoids.
Yeast gives us beer and bread. Now researchers have engineered it to do something more improbable: manufacturing the cannabis compounds CBD and THC.
Is Growing High-CBD Cannabis Different from Growing High-THC Cannabis?
If you’re thinking about growing hemp or high-CBD strains of cannabis in order to harvest the CBD, you may be wondering how similar the process is to growing cannabis for THC.
The process is remarkably similar, but not exactly the same.
On a biological and legal level, the only difference between hemp and high-CBD or high-THC cannabis plants is… the amount of THC and CBD. These are all simply different strains of the cannabis plant.
This plant in the front is a high-CBD strain of cannabis, with low levels of THC. Those plants in the back? They are all high-THC strains of cannabis. It’s hard to tell the difference, isn’t it? That’s because the only difference is the THC percentage.
Closeup of a bud on that same Critical+ CBD Auto plant
Hemp vs Cannabis vs Medical Marijuana: Like Different Strains of Roses
I look at my balcony and I have two rose bushes; a “Floribunda” and a “Fragrant Cloud”. They’re both strains of roses, but they grow differently and their flowers look and smell markedly different. The Floribunda grows lots of tiny orange roses that don’t have much of a smell, while the Fragrant Cloud makes just a few big hefty red roses that envelop the air with flowery perfume.
Each of these roses has their own “personality” but the actual plant care is basically the same. They get the same types of nutrients, watering, pruning, etc. This is basically what you’re looking at when it comes to different strains of cannabis, hemp or marijuana.
What is hemp and why is it legal?
Hemp was recently legalized on a federal level in the United States. But how is hemp different from cannabis?
There is exactly ONE difference between regular cannabis or marijuana and hemp….
The THC content. That’s it. You can have two strains of cannabis that look exactly the same, but if one contains less than 0.3% THC, it is considered hemp, while if it has even 0.4% THC by dry weight (in any part of the plant) it’s no longer considered to be hemp.
Learn more on the USDA government website (Excerpt: “The term ‘industrial hemp’ includes the plant Cannabis sativa L. and any part or derivative of the plant including seeds, whether or not it is used exclusively for industrial purposes (fiber and seed). The tetrahydrocannabinols (THC) concentration is the distinguishing factor between industrial hemp and marijuana. Industrial hemp cannot have a THC concentration more than 0.3 percent on a dry weight basis.”)
I know it seems like it should be more complicated than that, but that’s it. “Industrial hemp” is basically any strain of cannabis with extremely low levels of THC. The strains of hemp used by farmers typically have also been bred for a specific purpose such as providing fiber.
These plants are a type of industrial hemp. This cannabis strain has been selected to produce negligible amounts of THC and strong fibrous stalks.
How to Grow Cannabis or Hemp for CBD
If you want to grow your own CBD, the most important thing is to start with a high-CBD strain. You can’t force a cannabis plant to produce more CBD than its genes allow, and many if not most popular cannabis strains contain high levels of THC and less than 1% CBD. Genetics is key!
- Choose a high-CBD strain of cannabis.Note: if a plant contains more than 0.3% THC it is not considered hemp. If you’re concerned with THC percentages and making sure you’re growing hemp, it’s extremely important to get a strain from a trusted breeder.
- Grow mostly like typical cannabis. Here’s a 10-step guide to getting set up and growing your own cannabis. Here are tips for increasing CBD when growing cannabis.
- Pay attention to harvest time. For the highest levels of CBD, you should harvest plants at the beginning of the harvest window. Both CBD and THC start to degrade as buds continue to mature. If you harvest buds late there are a few differences. Buds harvested on the later side usually have slightly lower levels of CBD and THC, but higher levels of CBN. As a result, buds harvested later tend to be less psychoactive (due to less THC), and are more likely to make you feel sleepy or have a strong body effect (due to more CBN). Because of the various ways cannabinoids interact with each other, it’s important to experiment with harvesting early vs later to see what works best for you. Just because harvesting early gives the absolute highest level of CBD doesn’t mean the resulting buds will work the best for you. You should experiment with different harvest times because every body reacts differently!
- Keep the leaves. CBD is contained not just in the flowers/buds of the plant, but also in the leaves. The CBD concentration is relatively low so the leaves are not suitable to smoke, but the CBD can be extracted by turning the leaves into things like butter, tincture or oil. Note: CBD extractions made from leaves are typically less concentrated/strong than extractions made from the actual flowers/buds.
- Extracting CBD. Unlike the leaves, the CBD-rich buds/flowers are often smoked or vaped. However, many people prefer to consume them in some type of edible form. This has a slower onset but the effects tend to be longer-lasting. For the most part, any method that extracts THC will also extract CBD, as they’re both cannabinoids that easily attach to oil. The problem is you can’t easily separate THC and CBD from each other. So if the starting plant matter has no THC, then a simple extraction into butter/oil/tincture will extract the CBD. But if you’re trying to get just CBD from plant matter that has both THC and CBD, well you need equipment for that! This is why it’s so important you start with the right strain. If the plant produces only the cannabinoids you want, you don’t have to do anything but extract and enjoy them.
We’re currently testing various methods to further increase CBD levels when growing small hemp plants indoors. We’re also collaborating with experts to produce the best butters, oils, tinctures and CBD-rich candies so you have access to professional quality CBD sources at home. Stay tuned!
Is Growing High-CBD Cannabis Different from Growing High-THC Cannabis? If you’re thinking about growing hemp or high-CBD strains of cannabis in order to harvest the CBD, you may be wondering how