Particle production by algae

Résumé

The marine unicellular alga Emiliania huxleyi was cultivated in this study. Emiliania huxleyi is one of many species of the Coccolithophorida family, best known for their sophisticated biomineralization mechanisms through which they produce unique particle structures, known as coccoliths. Coccolith particles are composed of calcium carbonate and are formed intracellularly. After formation the particles are secreted and are fixated exocellularly in one or more layers, covering the entire cell. The main objective of this study was to produce those unique structures in freshly cultivated medium and latter recover them without damaging their structure. Clean recovered coccolith samples were afterwards characterized in an effort to better identify their particulate material properties. Recovery of a specific product is a challenging task, especially from biological systems where the composition does not remain constant. For the above purpose, Emiliania huxleyi cells were cultured continuously in fed-batch reactor systems to ensure adequate material quantities. To better understand the systems starting conditions a pre-treatment assessment was followed were the biogenic broth was characterized. Beneficial results assisted following cleaning processes, where coccolith particles were isolated. The cleaning processes were tested in cultivation broth from different runs which allowed comparison of the tested methods. The best cleaning concepts were optimized addressing thus the most important challenges that are faced in coccolith recovery. In the last part, clean coccoliths were characterized in respect to their particle size, surface chemistry and elemental composition. The acquired results supported a wetting behavior investigation which was estimated by the liquid penetration method according to the Washburn method. The results were compared with common calcium carbonate materials. Finally, the affect oblate particles have on particle size characterization techniques, has been reviewed for two clean coccolith samples.