Synthetic biologists have created an enzymatic network in yeast that turns sugar into cannabinoids, including tetrahydrocannabinol and cannabidiol, but also novel cannabinoids not found in the marijuana plant itself. The yeast factories would be more environmentally friendly and less energy intensive than growing the plant and separating out the psychoactive and non-psychoactive ingredients. They may also yield cannabinoid derivatives with unexpected medical uses.
Cannabis and its extracts, including the high-inducing THC, or tetrahydrocannabinol, are now legal in 10 states and the District of Columbia, and recreational marijuana -- smoked, vaped or consumed as edibles -- is a multibillion-dollar business nationwide. Medications containing THC have been approved by the Food and Drug Administration to reduce nausea after chemotherapy and to improve appetite in AIDS patients.
CBD, or cannabidiol, is used increasingly in cosmetics -- so-called cosmeceuticals -- and has been approved as a treatment for childhood epileptic seizures. It is being investigated as a therapy for numerous conditions, including anxiety, Parkinson's disease and chronic pain.
But medical research on the more than 100 other chemicals in marijuana has been difficult, because the chemicals occur in tiny quantities, making them hard to extract from the plant. Inexpensive, purer sources -- like yeast -- could make such studies easier.
Turning yeast into chemical factories involves co-opting their metabolism so that, instead of turning sugar into alcohol, for example, yeast convert sugar into other chemicals that are then modified by added enzymes to produce a new product, such as THC, that the yeast secrete into the liquid surrounding them. The researchers ended up inserting more than a dozen genes into yeast, many of them copies of genes used by the marijuana plant to synthesize cannabinoids.
See:
Xiaozhou Luo, Michael A. Reiter, Leo d’Espaux, Jeff Wong, Charles M. Denby, Anna Lechner, Yunfeng Zhang, Adrian T. Grzybowski, Simon Harth, Weiyin Lin, Hyunsu Lee, Changhua Yu, John Shin, Kai Deng, Veronica T. Benites, George Wang, Edward E. K. Baidoo, Yan Chen, Ishaan Dev, Christopher J. Petzold & Jay D. Keasling. Complete biosynthesis of cannabinoids and their unnatural analogues in yeast. Nature, 2019 DOI: 10.1038/s41586-019-0978-9
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
