4. Concluding remarks
The in vivo mRNA manufacturing system we have presented here can be utilised to produce synthetic mRNA molecules for a wide range of research and commercial applications. Although we have demonstrated for the first time that functional mammalian mRNA can be produced at high-yields in E. coli cell factories, widespread adoption of this platform requires further optimisation of both i) downstream processing steps to increase product purities and ii) upstream processes to maximise product titres by enhancing cell specific productivity and cell biomass accumulation/maintenance. While we anticipate that the developed system will be particularly suitable for production of circular mRNA products, it’s utility for manufacturing linear mRNA molecules would be significantly enhanced by optimising co-expression of a T7-Capping enzyme fusion protein (Qin et al., 2023) to enable synthesis of capped mRNA species in E. coli . Similarly, co-expression of nucleotide-modifying enzymes, such as Psuedouridine synthetase (Carlile et al., 2019), would permit production of linear mRNA products with required immunostimulatory properties for therapeutic applications.
The potential utility of microbial cell factories for large-scale mRNA manufacturing is being increasingly recognised. Indeed, earlier this year saw announcements of plans to develop commercial cell-based mRNA production processes using Eukaryotic cell-hosts. The availability of such platforms will become increasingly critical in coming years as product lines begin to diversify (e.g., adoption of more complex molecular formats) and the scale of global mRNA manufacturing continues to increase. By engineering the core components of an E. coli -based mRNA production system this study has added a novel technology to the mRNA manufacturing solution space, providing flexibility to achieve context- and/or application-specific design criteria.