Development of the high-productivity marine microalga, Picochlorum renovo , as a photosynthetic protein secretion platform

Microalgae are remarkable in their ability to convert CO2 and sunlight into renewable biomass and bioproducts. Here, we have established a novel photosynthetic protein production platform via computational prediction and genetic engineering using native microalgal protein secretory signal peptides to achieve functional secretion of the fluorescent protein mCherry. Importantly, this work was conducted in the recently characterized alga Picochlorum renovo, an alga of industrial interest due to its rapid growth rate, tolerance to both high temperature and salinity, and genetically tractable nuclear and chloroplast genomes. Genomic queries allowed the identification of native secretory signal peptides, which were N-terminally fused to mCherry allowing for secretion into the culture supernatant. Further characterization revealed no impact on fitness, a production rate of 0.19 mg/L/day, and titer of 0.37 mg/L of transgenic mCherry protein in culture supernatant. These findings lay the foundation for applied genetic engineering approaches that could enable CO2-sequestering, sustainable photoproduction of industrially relevant enzymes at low cost.

Automated summary

This study established a novel photosynthetic protein production platform in the industrial microalga Picochlorum renovo through computational prediction and genetic engineering, successfully achieving functional secretion of the fluorescent protein mCherry. Further characterization showed efficient production of transgenic protein in the culture supernatant.