Psilocybin is a tryptamine-derived psychoactive alkaloid found mainly in the fungal genus Psilocybe, among others, and is the active ingredient in so-called "magic mushrooms". Although its notoriety originates from its psychotropic properties and popular use as a recreational drug, clinical trials have recently recognized psilocybin as a promising candidate for the treatment of various psychological and neurological afflictions. In this work, we demonstrate the de novo biosynthetic production of psilocybin and related tryptamine derivatives in "brewers yeast" Saccharomyces cerevisiae by expression of a heterologous biosynthesis pathway sourced from Psilocybe cubensis. Additionally, we achieve improved product titers by supplementing the pathway with a novel cytochrome P450 reductase from P. cubensis. Further rational engineering resulted in a final production strain producing 627 +\- 140 mg/L of psilocybin and 580 +\- 276 mg/L of the dephosphorylated degradation product psilocin in triplicate controlled fed-batch fermentations in minimal synthetic media. Pathway intermediates baeocystin, nor norbaeocystin as well the dephosphorylated baeocystin degradation product norpsilocin were also detected in strains engineered for psilocybin production. We also demonstrate the biosynthetic production of natural tryptamine derivative aeruginascin as well as the production of a new-to-nature tryptamine derivative N-acetyl- 4-hydroxytryptamine. These results lay the foundation for the biotechnological production of psilocybin in a controlled environment for pharmaceutical applications, and provide a starting point for the biosynthetic production of other tryptamine derivatives of therapeutic relevance.

 

Controlled fed-batch fermentation results in higher titers. Production data from fed-batch fermentations of ST9482. Data is presented as averages from triplicate fermentations with standard deviations presented in shaded colours.

Psilocybin From Yeast - Interview with Nick Milne

More About Psilocybin

Psilocybin itself is actually not psychoactive. Once psilocybin is ingested, it is converted into psilocin, which causes the hallucinations. Alternative methods of psilocybin ingestion that avoid the digestive tract cause no hallucinations at all. Psilocin is particularly interesting because it is structurally similar to serotonin, an important neurotransmitter in the brain, and can bind with many of the same receptors. When psilocin binds to these receptors it causes many of the hallucinogenic effects of mushroom ingestion. But isolating psilocybin from mushrooms is expensive and there is high variability in the final product’s psilocybin concentrations. The most common magic mushroom contains 10-12 mg of psilocybin per gram of dried mushroom, and its effective oral dose is 6 to 20 mg. Variability among magic mushroom species in the quantity of psilocybin makes it difficult to implement effective moderation of doses for clinical treatments. This is currently a severe limiting factor for the implementation of treatments on a large scale.

It is because of this that research groups and biotechnology companies have been exploring alternative methods of production of psilocybin. Recently, COMPASS Pathway developed and patented a new method of isolating the compound through chemical synthesis, essentially creating psilocybin without the need of any mushrooms. This method can create pure psilocybin, but it uses a chemical called 4-hydroxyindole as a starting substrate. 4-hydroxyindole currently costs $224 USD per gram, making it a substantial financial barrier to running this process on larger scales.