Recovery of microalgal protein by three-steps membrane filtration: Advancements and feasibility

Microalgae are recognized as source of proteins for nutraceuticals, food additives and bioactive peptides. Also, the exploitation of the protein fraction can contribute to reach the profitability of the microalgal biorefinery. Among the available technologies, membrane filtration is one of the most sustainable and cost-effective technique for the protein recovery and purification. This study proposes a three-step filtration for the recovery, the purification and the concentration of proteins extracted from microalgal biomass. The selected microalgal strain was Chlorella sorokiniana. The proposed membrane process includes: 1) Prefiltration (0.22 μm – ceramic membrane) to remove cell fragments; 2) Diafiltration (0.22 μm – ceramic membrane) to recover the proteins retained in the first step; 3) Concentration (3 kDa – ceramic membrane) to concentrate the proteins and wash out salts and small sugars. The overall filtration process allowed the recovery of 12% of the initial proteins. The resulting proteins are uncoloured which suggests interesting industrial application. The reproducibility of the process was demonstrated by three different replicates. Finally, different strategies, for improving the economic viability of the refinery chain, have been proposed and discussed in the article.