Evaluation of Microalgae as Potential Sources of Antibacterial Activity

Bioactive secondary metabolites are known to be present in marine microalgae. This study examined the antibacterial activity of three specific microalgae: Oscillatoria acutissima, Oscillatoria simplicissima, and Spirulina platensis, and assessed their production of antibacterial compounds against various microbes. We investigated the effects of temperature, light intensity, and pH on the generation of antibacterial activity. Hexane, chloroform, ethanol, and methanol were used to prepare extracts from the selected algae, which were then tested for antibacterial compounds against microorganisms, including Aeromonas hydrophila, Micrococcus luteus, Salmonella spp., Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Vibrio spp., and Escherichia coli, as well as the yeast Candida albicans. The findings revealed that, under conditions of pH 8.0, 30ºC, and 3000 lux, the methanol extract exhibited significantly greater effectiveness against both fungal and bacterial strains compared to other extracts for all three algal strains. No antibacterial activity was detected in water extracts. The highest production of antibacterial compounds occurred after incubation periods of 12, 14, and 12 days in an aerated culture for Oscillatoria acutissima, Oscillatoria simplicissima, and Spirulina platensis, respectively. These results suggest that these microalgae have potential as producers of antibacterial agents.