Isolation and characterization of a Scenedesmus acutus strain to be used for bioremediation of urban wastewater

Abstract

Green microalgae, due to their short growth cycle and to their ability to photosynthetically fix carbon dioxide producing an oil-rich biomass, have been proposed as an attractive alternative feedstock for the production of “second generation” biofuels. However, it has been anticipated that owing to their ability to colonize very different environments characterized by high levels of nitrogen, they can also be good candidates for bioremediation, thus integrating environmental protection with sustainable biomass production. We have isolated a strain belonging to Scenedesmus genus from urban wastewater. This isolate, Scenedesmus acutus PVUW12, was tested for its ability to grow and actively deplete eutrophicating inorganic molecules present in wastewater. In order to test its biomass productivity, the PVUW12 strain was grown in a vertical-column photobioreactor using standard growth medium obtaining a maximal productivity of 0.3 g dry weight L−1 d. When the same strain was grown in the photobioreactor filled with wastewater collected from the final step of the local urban purifier plant containing 18.8 mg L−1 nitrate, we observed complete nitrogen removal coupled with a biomass production of about 0.74 g dry weight L−1 within 3 days. After 10 days, the recovered biomass was analyzed for triglyceride content which was found to be 9.3% of the dry biomass. However, when algal cells were left for additional 10 days in static conditions the triglyceride content increased to 28.8%. These data show that this Scenedesmus strain can be used for wastewater bioremediation producing a biomass suitable for energy production.