Antimicrobial activity of the acidophilic eukaryotic microalga Coccomyxa onubensis

Extremophilic microalgae are unexplored as a source of pharmaceuticals despite the fact that its biomass can be produced at large scale with low risk of contamination. A significant amount of antimicrobial activity was produced by extracts obtained from the eukaryotic acidophilic microalgae Coccomyxa onubensis in non-polar solvents, such as hexane, diethyl ether, and chloroform or in weakly polar solvents, such as dichloromethane, against Gram-negative and Gram-positive bacteria, and also the yeast Candida albicans. The most effective activity was shown by chloroform extract against Escherichia coli S, Salmonella enterica, and Proteus mirabilis; hexane extract against P. mirabilis, Sa. enterica, and Ca. albicans; dichloromethane extract against Sa. enterica or diethyl ether extract against E. coli S and the Gram-positive Staphylococcus aureus MB. The lowest minimum inhibitory concentration values were recorded against E. coli S (305 mu g mL(-1)) and P. mirabilis (153 mu g mL(-1)) (using chloroform extract) and against P. mirabilis (106 mu g mL(-1)) (using hexane extract). Fatty acids, but not carotenoids, seem to be involved in the antimicrobial activity of this microalga. However, further biochemical and biotechnological studies must be conducted in order to characterize and purify the bioactive principles from Co. onubensis for assessing its potential as a pharmaceutical source and feasibility of production.