Spirulina platensis, a cyanobacterium, attracted attention to many scientists due to its beneficial medicinal applications. Spirulina or its extracts are having several biological activities like anticancer, antiviral, antioxidant and antimicrobial activities. In the present study, antibacterial activity of Spirulina platensis solvent extracts was investigated against pathogenic bacteria. The antibacterial effect of ethanol, methanol, petroleum ether and extract of Spirulina platensis showed the antibacterial activities against different bacterial strains (Escherichia coli, Staphylococcus aureus, Salmonella typhi, Bacillus subtilis, Escherichia coli were tested, using disc diffusion method. Methanolic extract of Spirulina platensis showed maximum anti bacteriall activity of 15.0 mm against E. coli and a minimum activity of 9.0 mm against S. aureus and B. subtilis. Ethanolic extract of Spirulina platensis also showed the highest biological activity of 13.0 mm against Klebsiella pneumoniae), minimum activity of 9.0 mm against S. aureus and B. subtilis. The finding in this study reveals that antimicrobial activity of Spirulina platensis was highly effective in methanol the rest of the solvents showed varying degree of inhibition. Spirulina platensis showed maximum zone of inhibition against all the bacterial isolates.

Key words: Spirulina platensis, Antibacterial activity, Sargassum, bio fertilizer