Antibacterial activity, pigments, and biomass content of microalgae isolated from Greece

Microalgae display features that render them perfect candidates for biotechnological products and industrial applications. Nevertheless, still, only a small number of them have been studied for their metabolic potential. Herein, we aim to contribute to the microalgal metabolic diversity, including the study of novel genera and species that are investigated for the first time. The intracellular content of 30 eukaryotic autochthonous microalgae belonging to Chlorophyta, Bacillariophyta, Cercozoa, Heterokontophyta, and Rhodophyta isolated from different environments in Greece was extracted with six different solvents and tested for their antimicrobial activity against five pathogenic bacterial strains; > 50% of the extracts were found to inhibit the growth of the tested bacteria. Among extracts, methanol was found to be most effective followed by chloroform. Staphylococcus aureus and Pseudomonas aeruginosa have emerged as the most sensitive bacteria against algal extracts. Higher antibacterial activity was displayed by strains belonging to Chlorella vulgaris, Monoraphidium sp., Spongiosarcinopsis limneus, Chlorolilaea pamvotia, Microchloropsis gaditana, and Asterarcys quadricellularis. Strains growing in standard culture conditions, without applying any stress, were examined for their cellular content using analytical methods. The protein and carbohydrate content of some strains was relatively high. Desmodesmus sp., Spongiosarcinopsis limneus, Chlorolilaea pamvotia, Uronema trentonense, Akraea chliaropsychia, and Nomia picochloropsia strains displayed > 75% of their total cellular content comprising of the three compounds. We found strains worthy of further investigation to be used in commerce or as a potential material for biotechnology. Among strains that displayed a high concentration of valuable metabolic products, there are new algal genera and species, recently described such as Spongiosarcinopsis limneus, Chlorolilaea pamvotia and Akraea chliaropsychia from which new metabolic diversity emerges.