Production, concentration and purification of transparent exopolymeric particles (TEP) using paramagnetic functionalized microspheres

Xavier Mari, Hans G Dam

Limnol. Oceanogr. Methods 2:13-24 (2004) | DOI: 10.4319/lom.2004.2.13

ABSTRACT: We describe a new method to isolate and concentrate transparent exopolymeric particles (TEP), either naturally occurring or produced by phytoplankton in cultures. The principles of this method are to use TEP-sticking properties coupled with magnetic properties of paramagnetic microspheres to magnetically and selectively concentrate TEP. First, we studied the formation of mixed aggregates of TEP and 1-µm microspheres using the bubbling method. TEP precursors were obtained from diatom cultures and from natural seawater. Mixed aggregates of TEP–microspheres were efficiently formed—all TEP formed were associated with microspheres, and no clusters of microspheres alone were observed. The number of attached microspheres scaled with TEP size raised to an exponent of 1.53. The second step was to combine TEP with paramagnetic microspheres and isolate and concentrate the TEP by flowing out the solution containing mixed aggregates inside a strong magnetic field. About 90% of the magnetically labeled TEP were trapped inside the magnetic field. TEP volume concentration measured inside the magnetic field after isolation was about 5 times the initial TEP volume concentration. However, the predicted concentration factor, estimated from the relationship between number of attached microspheres versus TEP size, and the TEP size spectra in the initial solution was ~9. This suggests that TEP observed after isolation inside the magnetic field may be compacted and/or that a fraction of the TEP pool inside the magnetic field may remain glued to the inner walls of the culture flask and, thus, the observed TEP size spectra could be underestimated.