Fatty acids and their derivatives from <i>Chlorella vulgaris</i> extracts exhibit <i>in vitro</i> antimicrobial activity against the honey bee pathogen <i>Paenibacillus larvae</i>

The green microalga Chlorella vulgaris Beijerinck (Chlorellaceae) is widely used as a food supplement for humans and animals. In beekeeping practice, has potential pollen supplement. We studied whether extracts display antimicrobial properties against Paenibacillus larvae, the causative agent of honey bee bacterial disease American foulbrood. identified components responsible activity evaluated added values bees. Different (water, acetone, methanol) were prepared from biomass (phototrophically heterotrophically cultivated) screened ERIC I II genotypes P. larvae. Active acetone phototrophically cultivated fractioned via preparative reverse-phase chromatography. Antimicrobial was detected 9 resulting 33 fractions. Further analysis revealed chemical composition active C. showed significant effect vegetative cells spores larvae strains genotypes. lowest MIC most extract 6.3 µg/mL both tested majority fractions, monolinolenin, fatty acid linoleic acid, methyl esters and/or palmitic high-performance liquid chromatography coupled with high-resolution mass spectrometry analysis. Based on our results, we concluded that algal supplements not only contain nutritional but also prophylactic health.