Enhancement of phycoerythrin productivity in Porphyridium purpureum using the clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 ribonucleoprotein system

Genetic manipulation of the Porphyridium sp. may increase the production of phycoerythrin. Since phycobiliproteins capture and transfer energy to both photosystems (PS I and PS II), it was hypothesized that the gene mutation involved increases phycoerythrin synthesis. The gene encoding chlorophyll synthase (CHS1) was selected as chlorophyll synthase plays an important role in photosynthesis, mediating the final process of chlorophyll synthesis. Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 ribonucleoprotein (CRISPR/Cas9 RNP) delivery system was used to generate the chlorophyll synthase loss-of-function mutants (Δchs1). Independent Δchs1 showed no differences in the growth and production of sulfated polysaccharide compared to control. Phycoerythrin contents of the two independent mutants substantially increased regardless of light source. This study provides a novel applicability for the CRISPR/Cas9 RNP method in red microalgae toward a bio-product of interest. The obtained mutants could serve as potential producers of phycoerythrin if Porphyridium is selected as a natural source.