Bioengineering Phaeodactylum tricornutum, a marine diatom, for cannabinoid biosynthesis

Over the last few years, phytocannabinoids have been studied for their bioactive properties as potential drug candidates to treat or alleviate symptoms of several diseases. The isolation of single and pure cannabinoid (CB) from their natural source, i.e., Cannabis plants results in a low yield, diluted among hundreds of other plant metabolites. The use of biotechnological platforms to produce single CBs is appealing to the pharmaceutical industry. Therefore, our aim was to develop a sustainable system using the model diatom Phaeodactylum tricornutum to produce cannabigerolic acid (CBGA), the precursor to several CBs such as well-known cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC). We engineered P. tricornutum to express a mutant version of the Streptomyces sp. strain CL190's naptherpin biosynthetic cluster gene B NphB (Y288A/G286S, nphB), a nonCannabis aromatic prenyltransferase enzyme, either by random integrated chromosomal expression (RICE) or extrachromosomal expression (EE), to maximize the success of protein production. The gene of nphB was linked to the reporter cyan fluorescent protein (CFP) and introduced in P. tricornutum. Clones were characterized by CFP fluorescence intensity, protein synthesis, enzymatic activity, and production of CBGA. We present, for the first time in diatoms, the successful production of a CB, CBGA up to 4.1 (+/- 0.2) mg/kg of microalgal fresh biomass weight. This work shows the potential of P. tricornutum as a sustainable controlled heterologous platform for CBs production, plant bioactive compounds, and relevant pharmaceuticals.