Antimicrobial and Antioxidant Property of Commonly Found Microalgae Spirulina Platensis, Nostoc Muscorum and Chlorella Pyrenoidosa against Some Pathogenic Bacteria and Fungi

In the present study, three algal species (Spirulina platensis, Chlorella pyrenoidosa and Nostoc muscorum (ATCC 2789) were used to investigate their antimicrobial and antioxidant properties against some human pathogenic bacteria and fungi (Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Micrococcus luteus and fungus Aspergillus luchuensis, Aspergillus niger, Fusarium oxysporum). Four different solvents namely methanol, acetone, nhexane and water were used for extraction. The present investigation showed that methanolic extract was more effective against the pathogenic bacteria and fungi. Methanolic extract of C. pyrenoidosa and N. muscorum was found to be most effective against P. aeruginosa while methanolic extract of S. platensis showed maximum activity against S. aureus. S. platensis showed maximum antifungal activity in comparison to other algal extracts. Antioxidant activity was determined by free radical scavenging activity (Nitric oxide radical scavenging activity) and it was found that methanolic extract of S. platensis showed maximum antioxidant activity. INTRODUCTION: Algae are photosynthetic organisms, which constitute a total of twenty-five to thirty thousand species, with a great diversity of forms and sizes ranging from unicellular microscopic organisms (microalgae) to multicellular organisms of great size (macroalgae). They can double every few hours during their exponential growth period . During the peak growth phase, some microalgae can double even every 3.5 hrs . In fact, some algae are organisms that live in complex habitats submitted to extreme conditions as they can easily adapt to the new environmental conditions and are known to produce a great variety of secondary (biologically active) metabolites, which cannot be found in other organisms . Algae can be a very interesting natural source of new compounds with biological activity that could be used as functional ingredients . Seaweeds represent a potential source of antimicrobial substances due to their diversity of secondary metabolites with antiviral, antibacterial and antifungal activities 5, . The search for similar antimicrobial activity in other algal species has gained importance in recent years due to growing worldwide concern about antibioticresistant micro-organisms. Efforts are being made to extract substances with antibacterial, antiviral, fungicidal, enzyme inhibitory, immunosuppressive and cytotoxic and algicidal property from the low cost algal biomass .