Evaluation of antimicrobial activity of different extracts of microalga, Chlorella sp., grown under autotrophic condition

Regarding increasing rate of drug resistance among microbial pathogens, a global search to find new antimicrobials from natural compounds with fewer side effects has been considered by researchers. The aim of the current study was to evaluate antimicrobial effects of different extracts of the microalga Chlorella sp. grown under autotrophic condition. Algal cultivation was performed in Zinder medium and the biomass was harvested at the end of log phase. Different extracts were prepared using acetone, chloroform, hexane, ethyl acetate and hexane-acetate as extraction solvents and antimicrobial activity of the extracts was investigated against two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and a fungal strain (Candida albicans). Antimicrobial activity of the extracts was determined by measuring the zone of inhibition (ZOI) using well-diffusion method. According to the results, the chloroform and ethyl acetate mediated extracts showed the highest antimicrobial activity compared to the other extracts. In conclusion, Chlorella sp. extracts show good antimicrobial activity and antimicrobial efficacy depends on extraction solvents.