Biological Activity of Endometabolites of Microalgae Chlorella sorokiniana

Abstract

Microalgae metabolites exhibit significant biological activity and can act as antibacterial agents (peptide and lipid fraction) against Gram-positive bacteria Bacillus and as a component of nutrient media in the cultivation of yeast Saccharomyces cerevisiae. In this study, a mixture of metabolites (triacylglycerides, fatty acids, o-dialkylmonoglycerides and glycerol trialkyl esters) extracted from disrupted Chlorella sorokiniana microalgae cells by non-polar solvent had inhibitory effect on the growth of Gram-positive bacteria at photosynthetically active radiation (PAR) levels of 100 ± 6 μmol photons/(m²·s). The minimum inhibitory concentration (MIC) of the extract was ≈80 μg/mL. Out of the isolated components of the mixture, triacylglycerides and fatty acids showed antibacterial properties, with MIC = 176 μg/mL and MIC = 445 μg/mL respectively. The water-soluble peptide fraction extracted from microalgae cells had an inhibitory effect on the growth of Gram-positive bacteria Bacillus both under white light illumination and in the dark; MIC of the peptide fraction is ≈125 μg/mL (when illuminated) and 170 μg/mL (in the dark). The water-soluble protein fraction had no antibiotic properties, but is of interest as a component of nutrient medium (0.01 mL/mL) for the cultivation of yeast Saccharomyces cerevisiae. The addition of this fraction allowed a 21% increase in population capacity compared with the control sample, a 1.4-fold increase in the specific growth rate in the exponential phase and a 28% decrease in cell generation time. The study has contributed to establishing the effect of light radiation on antibacterial properties of microalgae metabolites and identifying the minimal inhibitory concentration with regard to Gram-positive bacteria. Also, the potential of the Chlorella aqueous extract to serve as a component of nutrient media for the Saccharomyces cerevisiae cultivation has been researched.