Antimicrobial activity of <i>Chlorella sorokiniana</i> ethyl acetate extract

Antimicrobial resistance is a growing global problem requiring urgent action. A potential solution is to investigate underexplored microorganisms from unique environments for the production of antimicrobials. The aim of this study was to investigate the antibacterial properties of Chlorella sorokiniana, a microalga in the marine environment. The microalga was isolated and identified by scanning electron microscopy (SEM) and confirmed by molecular method. Antimicrobial activities of the cell-free-supernatant (CFS) and ethyl acetate extract of the microalga were investigated against typed cultured bacteria [Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923)] using agar well diffusion method, while the analysis of bioactive constituents of the CSF and the extract was carried out using Gas Chromatography-Mass Spectrometry (GCMS). The extracts of C. sorokiniana displayed excellent antimicrobial activities on both bacteria with a range of 17.00 – 18.00mm zone of inhibition at 1.67 µl while the CFS showed no inhibition. A total of ten bioactive constituents were identified, notably dominated by fatty acids such as lauric, decanoic, oleic and tetradecanoic acids which were suspected to be partly responsible for the observed broad-spectrum of antimicrobial effect in this study. The findings of this study suggest C. sorokiniana is a potential natural source of antimicrobial agent for the treatment of bacterial infections.