Evaluation of electroflocculation harvesting on the antioxidant activity and toxicity of extracts from the microalgae Isochrysis galbana and Phaeodactylum tricornutum

The harvesting method is a challenge in microalgae production since it may influence the bioactivity of the product. This study aimed to evaluate if electroflocculation biomass harvesting altered the antioxidant properties and toxicity of methanol extracts from the marine microalgae Isochrysis galbana and Phaeodactylum tricornutum, compared with the traditional centrifugation approach. Analyses were based on the elimination of the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) free radical by the active ingredients from the extracts, thin-layer chromatography (TLC), calculation of IC50, and extract toxicity. Phaeodactylum tricornutum had similar DPPH-reactive fractions (with antioxidant activity) different from the β-carotene control in the TLC for both biomass-separating methods, but its IC50 was 63% higher for electroflocculation (lower antioxidant activity). Bands with antioxidant activity were absent in the TCL of I. galbana (non-DPPH-reactive) for both harvesting methods. The extracts did not present mortality for the study with the Artemia salina model. Therefore, electroflocculation can produce up to 10 times more biomass without cytotoxicity output but may decrease the antioxidant potential of microalgae extracts.