Analysis and evaluation of methods used for harvesting microalgae from culture media and suitable for Porphyridium purpureum

This article reviews modern methods for harvesting microalgae biomass from culture media, explores their advantages and limitations, as well as argues that the choice of an optimal and efficient method depends on the scale of production, the types of microalgae, and the composition of culture media. Here, the methods of centrifugation, gravity sedimentation, and separation were evaluated for their efficiency in the recovery of Porphyridium purpureum cells. During the experiments, separation outperformed the other two methods in terms of the resulting biomass dry weight and the time consumed. When applied to Porphyridium purpureum , it yielded 20.75 g of dry biomass by processing a 100 times larger volume of the suspension at 1 kW of energy input, thus demonstrating a fivefold increase in overall efficiency compared to centrifugation. To achieve a high biomass concentration ratio and reduce energy costs in the recovery of P. purpureum , a multi-stage harvesting process, combining initial gravity sedimentation with either centrifugation or separation, was proposed. The findings can serve as the basis for developing practical guidelines on selecting an optimal strategy for large-scale harvesting of microalgae.