Study on high-CO₂ tolerant Dunaliella salina and its mechanism via transcriptomic analysis

Microalgae has been regarded as a promising method for reducing CO₂ emission. High CO₂ concentration generally inhibits algal growth, and previous studies have mostly focused on breeding freshwater algae with high CO₂ tolerance. In this study, one marine algal strain Dunaliella salina (D. salina) was grown under 0.03%-30 % CO₂ and 3% NaCl conditions, and was evaluated to determine its potential for CO₂ assimilation. The results showed that D. salina could tolerate 30% CO₂ , and its maximum biomass concentration could reach 1.13 g·L^-1 after 8 days incubation, which was 1.85 times higher than that of incubation in air (0.03%). The phenomenon of high-CO₂ tolerance in D. salina culture was discussed basing on transcriptome analysis. The results showed that D. salina was subjected to oxidative stress under 30% CO₂ conditions, and the majority genes involving in antioxidant system, such as SOD, CAT, and APX genes were up-regulated to scavenge ROS. In addition, most of the key enzyme genes related to photosynthesis, carbon fixation and metabolism were up-regulated, which are consistent with the higher physiological and biochemical values for D. salina incubation under 30% CO₂ .