Synthetic biologists from the University of California at Berkeley have manufactured beer yeast to produce the main ingredients of marijuana – mind-altering THC and non-psychoactive CBD – as well as new cannabinoids not present in l & # 39; plant.
By eating only sugar, yeasts are an easy and inexpensive way to produce pure cannabinoids that it is now expensive to extract buds from the cannabis plant, Cannabis sativa.
"For the consumer, the benefits are high quality CBD and THC at low cost: you get exactly what you want from yeast," said Jay Keasling, professor of chemical and biomolecular engineering at the University of California. Berkeley, and researcher in teaching at the university. Lawrence Berkeley National Laboratory. "It's a safer and more environmentally friendly way to produce cannabinoids."
Cannabis and its extracts, including THC, or tetrahydrocannabinol, a highly inducing factor, are now legal in 10 states and in the District of Columbia. Marijuana for recreational purposes – smoke, consumed or consumed for food – represents a multi-billion dollar business nationwide. THC-containing medications have been approved by the Food and Drug Administration to reduce nausea after chemotherapy and improve the appetite of AIDS patients.
CBD, or cannabidiol, is increasingly used in cosmetics – what is called cosmeceuticals – and has been approved as a treatment for epileptic seizures in children. It is being studied as a treatment for many conditions, including anxiety, Parkinson's disease and chronic pain.
But medical research on more than 100 other chemicals found in marijuana has been difficult because the chemicals are present in minute amounts, making them difficult to extract from the plant. Low cost and more pure sources – such as yeast – could facilitate such studies.
In addition, he added, there is "the possibility of new therapies based on new cannabinoids: the few that are almost impossible to obtain from the plant, or the unnatural substances, which are impossible to obtain from the plant. ".
Keasling, the chair of the Philomathia Alternative Energy Foundation at Berkeley, and his colleagues will report their findings online on February 27, before being published in the newspaper. Nature.
Connect the chemical pathways in yeast
Cannabinoids are found in many other chemicals and drugs currently produced in yeast, including human growth hormone, insulin, blood clotting factors and, recently, but not yet on the market, morphine and other opiates.
Keasling, one of the pioneers of synthetic biology, has long sought to harness yeasts and bacteria as "green" drug factories, eliminating the expensive routine synthesis or extraction processes in the world. 39 chemical industry and chemical by-products often toxic or damaging to the environment.
Cannabis cultivation is an excellent example of an energy-intensive and environmentally destructive industry. Farms in northwestern California polluted waterways with pesticide and fertilizer runoff and helped drain watersheds because marijuana plants consume a lot of water . Illegal crops have led to clearcuts and erosion.
Indoor growing with ventilation fans consumes a lot of energy, accounting for a growing percentage of annual energy consumption. One study estimated that the cannabis industry in California accounted for 3% of the state's electricity consumption. Indoor growth has caused power outages in some cities, and energy consumption can add more than $ 1,000 to the price of a pound of weeds.
Hence the interest of Keasling to find a "green way" to produce the active chemicals contained in marijuana.
"It was an interesting scientific challenge," he admitted, which was related to other challenges that he and his team have overcome with yeast: producing an antimalarial drug, l & # 39; artemisinin; transform plant waste into biofuels; synthesize aromas and fragrances for the food and cosmetics industries and chemical intermediates for the manufacture of new materials. "But when you read articles about patients with seizures and help from CAD, especially children, you realize that these molecules are valuable, and that producing cannabinoids in yeast could really be great."
With the approval and control of the US Drug Enforcement Agency – cannabis is still illegal under federal law – postdoctoral fellow Berkeley Xiaozhou Luo and visiting graduate student Michael Reiter, who led the project , began to assemble in yeast a series of chemical steps to initially produce the mother of all cannabinoids, CBGA (cannabigerolic acid). In marijuana and yeast, chemical reactions involve the acid form of the compounds: CBGA and its derivatives, THCA and CBDA. They easily convert to CBG, THC and CBD when exposed to light and heat.
Transforming yeast into chemical plants involves co-opting one's metabolism, so that yeast, instead of turning sugar into alcohol, converts the sugar into other chemicals that are then modified by the addition of sugar. Enzymes to produce a new product, such as THC, so that the yeast secrete into the fluid that surrounds them. The researchers eventually inserted more than a dozen genes into the yeast, many of which were copies of genes used by the marijuana plant to synthesize cannabinoids.
One step, however, has proven to be an obstacle for the Keasling Group and its competing groups: an enzyme that performs a key chemical step in the manufacture of CBGA in the marijuana plant does not work in yeast.
Rather than creating a different route of synthesis, Berkeley's postdoctoral fellow, Leo d'Espaux, and graduate student Jeff Wong, returned to the plant and isolated a second enzyme, prenyl transferase, which same thing and blocked it in the yeast.
"It worked like gangbusters," Keasling said.
Once they had CBGA producing yeast, they added another enzyme to convert CBGA to THCA and a different enzyme to create a pathway leading to CBDA. Although the products produced by yeast are mainly THC or CBD, Keasling said, each must be separated from other chemicals present in minute quantities.
They also added enzymes that allowed the yeast to produce two other natural cannabinoids, CBDV (cannabidivarin) and THCV (tetrahydrocannabivarin), the effects of which are not well understood.
Surprisingly, Xiaozhou and Michael have discovered that the enzymatic steps required to make CBGA in yeast are flexible enough to accept a variety of starting chemicals – different fatty acids from those used by the marijuana plant, the l? hexanoic acid – which generate cannabinoids that do not exist in the plant itself. They also asked the yeast to incorporate chemicals into cannabinoids that could then be chemically modified in the laboratory, creating another way to produce unprecedented but potentially medically useful cannabinoids.
Keasling then founded a company, Demetrix Inc., in Emeryville, Calif., Which was later joined by Espaux and Wong, which allowed Berkeley's technology to use yeast fermentation to make cannabinoids.
"The economic conditions are really good," said Keasling. "The cost is competitive or better than that of cannabinoids derived from plants, and manufacturers do not have to worry about contamination – for example, THC in the CBD – that would make you high."