Knockout of Cia5 gene using CRISPR/Cas9 technique in Chlamydomonas reinhardtii and evaluating CO2 sequestration in control and mutant isolates

CRISPR/Cas9 technology is one of the common methods of genome editing and targeted gene mutation, which has recently been used for manipulating microalgae such as Chlamydomonas reinhardtii . Besides, this technology can play a role in the fight against greenhouse gases (e.g., carbon dioxide) production by studying genetic pathways to improve algal strains. Among several genes in algae that respond to CO 2 and regulators control the expression of each; Cia5 is one of the most critical transcriptional regulators. In this research, we knocked out the Cia5 gene using the CRISPR/Cas9 technique and analysed the ability of C. reinhardtii to perform CO 2 sequestration. Our results showed that C. reinhardtii has better performance (i.e., response to CO 2 treatment) in both control and mutant species at 0.5% CO 2 concentration than other concentrations. However, the difference between the control microalgae species and the mutant species was in the CO 2 removal efficiency. Additionally, our findings revealed that the control type isolate in CO 2 concentrations of 0.04%, 0.5% and 1% had removal efficiencies of 27%, 37% and 21%, respectively. Nevertheless, for mutant species in the same concentrations, the observed removal efficiencies were 16%, 23% and 9%.