Inorganic salt starvation improves the polysaccharide production and CO₂ fixation by Porphyridium purpureum

The microalgae industry shows a promising future in the production of high-value products such as pigments, phycoerythrin, polyunsaturated fatty acids, and polysaccharides. It was found that polysaccharides have high biomedical value (such as antiviral, antibacterial, antitumor, antioxidative) and industrial application prospects (such as antioxidants). This study aimed to improve the polysaccharides accumulation of Porphyridium purpureum CoE1, which was effectuated by inorganic salt starvation strategy whilst supplying rich carbon dioxide. At a culturing temperature of 25 °C, the highest polysaccharide content (2.89 g/L) was achieved in 50% artificial seawater on the 12th day. This accounted for approximately 37.29% of the dry biomass, signifying a 25.3% increase in polysaccharide production compared to the culture in 100% artificial seawater. Subsequently, separation, purification and characterization of polysaccharides produced were conducted. Furthermore, the assessment of CO₂ fixation capacity during the cultivation of P. purpureum CoE1 was conducted in a 10 L photobioreactor. This indicated that the strain exhibited an excellent CO₂ fixation capacity of 1.66 g CO₂/g biomass/d. This study proposed an efficient and feasible approach that not only increasing the yield of polysaccharides by P. purpureum CoE1, but also fixing CO₂ with a high rate, which showed great potential in the microalgae industry and Bio-Energy with Carbon Capture and Storage.