Screening microalgae for some potentially useful agricultural and pharmaceutical secondary metabolites

Nearly two hundred microalgal strains (174 Chlorophyta and 23 Cyanobacteria) were screened against some bacteria, filamentous fungi and yeasts using a disc-diffusion type bioassay. From this initial screening, 10 Chlorophyta strains from three genera (Desmococcus, Chlorella and Scenedesmus) were selected because of their high antimicrobial activity. These 10 strains were partially purified and tested using MIC antimicrobial and microtiter IC₅₀ anticancer assays. These preselected algal strains showed a high incidence of antibacterial activity against both Gram-positive (9 out of 10 species) and Gram-negative (7 out of 10 species) bacteria. The extracts were also effective against some tumour cell lines.