Screening of antiviral activity in freshwater and marine microalgae: Inactivation capacity over enveloped and non-enveloped viruses

New viruses are one of the major health challenges that human society is facing during this century. One of the most promising solutions is searching for natural organisms or molecules with antiviral capacity, with emerging microalgae as a promising solution in recent years. Thus, in this work, the antiviral capacity of ten species of freshwater and marine microalgae was tested against three enveloped and non-enveloped bacteriophages (PhiX174, MS2 and Phi6), showing inhibition efficiencies ranging from 40 to 80% compared with control infections. Moreover, the PCA analysis revealed the influence of the microalgal cell wall on the different bacteriophages' inactivation capacity. Finally, the inactivation of the three bacteriophages in liquid cultures was studied using the microalgae Chlorella vulgaris and Thalassiosira weissflogii. These microalgae inactivated 99.999% of the MS2 and Phi6, and 99.9% of PhiX174 after 72 h of cultivation, respectively. Additionally, T₉₀ values ranging from 7 to 12 h for PhiX174, 3 to 12 h for MS2 and 2.5 to 3 h for Phi6 were achieved by the two tested microalgae. These results highlight the potential of microalgae for the inactivation of viruses in wastewaters and as an outstanding source of antivirals.