Researchers have reported that the microalgal chloroplast has clear potential as a novel industrial production platform for biopharmaceuticals. The continued development of synthetic biology tools for chloroplast engineering of C. reinhardtii will strengthen this potential by accelerating the creation of designer transgenic lines yielding high levels of the target protein.

Currently, the industrial biotechnology sector is almost exclusively based around the use of heterotrophic platforms (bacteria, yeasts, mammalian and insect cells) for the biosynthesis of pharmaceutical proteins, bioactive metabolites or other high-value products.

However, the ever-increasing growth of the global bioeconomy and the need for sustainable alternatives to petrochemical-based products is catalyzing interest in the exploitation of alternative cell factories, including photosynthetic microalgae and cyanobacteria.

Microalgae represent a significant untapped potential for bio-manufacturing because of the extreme biodiversity of the >70 000 extant species spread over the eukaryotic tree of life. Of these species, the freshwater chlorophyte Chlamydomonas reinhardtii is perhaps the most advanced microalgal platform.

Chlamydomonas reinhardtii is suitable for molecular tools for both nuclear and chloroplast transformation, and the ongoing development of synthetic biology strategies for strain engineering. The chloroplast of Chlamydomonas reinhardtii and other microalgae represents an attractive new platform for the synthesis of recombinant therapeutics using synthetic biology (synbio) approaches.

In the short review the research outline the current status and merits of algal chloroplast transgenics, and survey the different classes of therapeutics being produced for either human or livestock applications. The team also consider the future development of synthetic biology tools to accelerate the predictive design and creation of bespoke strains.

Transgenes can be designed in silico, assembled from validated DNA parts and inserted at precise and predetermined locations within the chloroplast genome to give the stable synthesis of a desired recombinant protein.

Numerous recent examples of different therapeutic proteins produced successfully in the C. reinhardtii chloroplast highlight the potential of this green alga as a simple, low-cost and benign host. Furthermore, some of the features of the alga may offer additional advantages over more-established microbial, mammalian or plant-based systems.

These include efficient folding and accumulation of the product in the chloroplast; a lack of contaminating toxins or infectious agents; reduced downstream processing requirements; the possibility to make complex therapeutics such as immunotoxins; and the opportunity to use the whole alga as a low-cost oral vaccine.