Extraction Optimization of Polysaccharides from Wet Red Microalga Porphyridium purpureum Using Response Surface Methodology

<i>Porphyridium</i> is a unicellular marine microalga that is rich in polysaccharides and has excellent biological activities. Optimizing the extraction of polysaccharides can significantly improve the value of <i>Porphyridium</i> biomass. In the present study, response surface methodology was employed to optimize the extraction conditions of polysaccharides, including extraction time, extraction temperature, and biomass-to-water ratio. Furthermore, microwave-assisted extraction was used to improve the yield of polysaccharides further. The results showed that increasing the extraction temperature and extraction time could enhance the yield of polysaccharides. The multiple regression analysis of RSM indicated that the model could be employed to optimize the extraction of polysaccharides. The optimal extraction time, extraction temperature, and biomass-to-water ratio were 45 min, 87 °C, and 1:63 g mL^-1, respectively. Under these optimal conditions, the maximum yield of polysaccharides was 23.66% DW, which well matched the predicted yield. The results indicated that the extraction temperature was the most significant condition affecting the yield of polysaccharides. The microwave-assisted extraction could further improve the yield of polysaccharides to 25.48% DW. In conclusion, hot water with microwave-assisted extraction was effective for polysaccharide extraction in <i>P. purpureum</i>.