Developing a nanocellulose-based reversible flocculant for harvesting microalgae through better understanding of the interaction between the flocculant and the microalgal cell surface

Microalgae are a promising new source of biomass that can be used for energy, feed, food or various high value applications. A challenge in microalgae production is the harvesting, which requires separating the microalgal cells from the liquid cultivation medium. Microalgae can be harvested by aggregating individual small cells into flocs that settle down spontaneously. Yet, this requires addition of a chemical flocculant that ends up in and contaminates the biomass. In this project we want to develop a reversible flocculant that can be removed from the biomass after harvesting and that can be re-used. This flocculant will be based on cellulose, an abundantly available bio-based resource. We will use cellulose nanoparticles to construct this flocculant and modify it with pH-responsive groups that bind to the microalgae and induce flocculation at low pH, but can be removed at high pH. To create these cellulose nanomaterial, we need to understand the mechanism through which such nanomaterials interact with the surface of the microalgal cells. Therefore, we will investigate the chemistry and surface properties of microalgal cells and model the interaction of modified nanocellulose with the microalgal cell surface. We will use atomic force spectroscopy as a high end tool to actually measure the interaction between the modified nanocellulose and microalgal cells.