Mouse Bioassay Acute and Subchronic Safety Assessment of Biomass from Swine Wastewater Phycoremediation

Abstract

Swine wastewater is nutrients-rich (N and P) and also may contain toxic environmental contaminants. Both nutrients and contaminants can be removed by microalgae-based treatment (phycoremediation) and the harvested biomass from this process has the potential to be used as animal feed, provided that safety precautions are taken. We have assessed the acute and subchronic toxicity of microalgae biomass harvested from swine effluent digestate by mouse bioassays. Acute toxicity tests (14 days) were carried out with the mice receiving microalgae extracts at doses of 1500 and 2500 mg kg−1 i.p. and 2500 mg kg−1 orally. Subchronic toxicity tests (30 days) were performed with the mice fed orally with 1500 and 2500 mg kg−1 doses. Clinical-behavioral signs, body and organ weight gain, and water and feed intake were monitored. Administration of the microalgae extract at 1500 mg kg−1 and 2500 mg kg−1 i.p. doses resulted in deaths of 20 and 60%, respectively. Oral intake in the acute test caused none deaths and signs of toxicity were not observed. Subchronical administration of 1500 mg kg−1 dose proved safe, while 2500 mg kg−1 dose showed up low toxicity with 25% lethality. Microalgae biomass resulted from swine wastewater phycoremediation, due to it is nutritional content and versatile biochemical composition, can be a valuable source with high application potential. However, the definition of safety margins through toxicity assessments for more noble uses, such as animal feed, is an extremely important step in this process.