Virucidal activity of microalgae extracts harvested during phycoremediation of swine wastewater

Phycoremediation of swine wastewater is a promising treatment since it efficiently removes nutrients and contaminants and, simultaneously, its biomass can be harvested and used to obtain a wide range of valuable compounds and metabolites. In this context, biomass microalgae were investigated for the phycoremediation of swine wastewater, and biomass extracts for its virucidal effect against enveloped and non-enveloped viruses. Microalgae were cultivated in a pilot scale bioreactor fed with swine wastewater as the growth substrate. Hexane, dichloromethane, and methanol were used to obtain the microalgae extracts. Extracts were tested for virucidal potential against HSV-1 and HAdV-5. Virucidal assays were conducted at temperatures that emulate environmental conditions (21 °C) and body temperature (37 °C). The maximum production of microalgae biomass reached a concentration of 318.5 ± 23.6 mg_DW L^-1. The results showed that phycoremediation removed 100% of ammonia-N and phosphate-P, with rates (k₁) of 0.218 ± 0.013 and 0.501 ± 0.038 (day^-1), respectively. All microalgae extract reduced 100% of the infectious capacity of HSV-1. The microalgae extracts with dichloromethane and methanol showed inhibition activities at the lowest concentration (3.125 µg mL^-1). Virucidal assays against HAdV-5 using microalgae extract of hexane and methanol inhibited the infectious capacity of the virus by 70% at all concentrations tested at 37 °C. At a concentration of 12.5 µg mL^-1, the dichloromethane microalgae extract reduced 50-80% of the infectious capacity of HAdV-5, also at 37 °C. Overall, the results suggest that the microalgae can be an attractive source of feedstock biomass for the exploration of alternative virucidal compounds.