Residual biomasses and protein hydrolysates of three green microalgae species exhibit antioxidant and anti-aging activity

It is widely recognized that microalgae represent a promising strategy in the development of next-generation biofuels; however, their economic viability remains questionable. Several studies have shown microalgal biomass is a relatively unexplored source of natural components with nutraceutical activities; indeed, some authors state that the remaining residue after oil extraction from the microalgae biomass, known as microalgae residual biomass (MRB), could have outstanding biological activities. Therefore, in the present study, we analyzed the antioxidant capacity and anti-aging potential of MRB and protein hydrolysates of three green microalgae species: Dunaliella tertiolecta, Tetraselmis suecica, and Nannochloropsis sp. Antioxidant capacity, determined through oxygen radical absorbance capacity (ORAC), radical cation activity (ABTS), and radical scavenging activity (DPPH), of the three MRBs was good overall, with D. tertiolecta and Nannochloropsis having the highest antioxidant capacity. Interestingly, their protein hydrolysates showed markedly higher antioxidant capacities than their MRBs at the concentrations tested. Anti-aging potential, determined by the inhibition of the activity of two extracellular matrix-degrading enzymes, elastase and hyaluronidase, was found to be higher in D. tertiolecta and Nannochloropsis biomasses for anti-elastase activity; however, no significant differences between microalgae species were found in anti-hyaluronidase activity. For the protein hydrolysates, Nannochloropsis had the highest anti-elastase and anti-hyaluronidase activity. In conclusion, selected MRBs and their protein hydrolysates exhibited a good antioxidant capacity and/or anti-aging potential overall, indicating the economical importance of MRBs in the nutraceutical and nutricosmetic industries. Overall, this study contributes to convert microalgae biofuel production into a more sustainable and economically feasible process, through the comprehensive utilization of residual biomass.