Influence of harvesting method on biomass yield and antimicrobial activity of Isochrysis galbana and Phaeodactylum tricornutum extracts

Microalgae are recognized as promising sources of high-value bioactive compounds with applications in agricultural and pharmacological industries; however, conventional biomass harvesting methods may reduce yield, compromise bioactivity, and increase processing costs. This study aimed to evaluate the effect of electroflocculation on biomass recovery and the preservation of antimicrobial activity of microalgal extracts, in comparison with centrifugation. Cultures of both species were harvested using electroflocculation and centrifugation, followed by biomass quantification and extraction of bioactive compounds. The antibacterial activity of the extracts was assessed against bacterial strains of clinical and industrial relevance, allowing a comparative evaluation of harvesting efficiency and bioactivity preservation. Electroflocculation resulted in higher biomass recovery compared to centrifugation for both microalgal species. In addition, extracts obtained from electroflocculated biomass exhibited higher antibacterial activity under the tested conditions, indicating improved preservation of bioactive compounds during the harvesting process. These findings demonstrate that electroflocculation is a clean, efficient, and sustainable method for microalgal biomass harvesting, suggesting advantages over conventional centrifugation in terms of yield and maintenance of antimicrobial activity, and supporting its application in biotechnological processes aimed at producing bioactive compounds from microalgae.