Antimicrobial activity of macroalgal extracts against several Listeria monocytogenes strains for the application in food production

Macroalgae are a source of compounds used for a long time in human affairs; some algal species are more used than others, as they possess molecules with antibacterial, antiviral, antifungal and immunostimulant activity. These molecules are often extracted from algal species which are invasive and, therefore, their use is also advisable in the perspective of environmental management, to eliminate large unwanted biomasses. In the present research, we evaluated the antimicrobial activity of Asparagopsis extracts against different Listeria monocytogenes strains. Ethanolic extracts prepared from lyophilized algal material were tested against 6 different strains of Listeria monocytogenes: 3 ATCC (13932, 7644, 1911) and 3 wilds isolates from food matrix. A mean value of 22±5 mm was reported for all the strains with the disk-diffusion assay (disk 6 mm) of the extracted compound. Furthermore, the Minimal Inhibiting Concentration (MIC) and Minimal Bactericidal Concentration (MBC) were performed by microdilution method. A value of 0.05% was established for all strains both for MIC and MBC. These results represent a very promising finding for the application of Asparagopsis extracts in food production as natural preservatives against Listeria monocytogenes.