Electron Microscopy of Fresh and Dried Cells of Chlorella Pyrenoidosa

Abstract

Photosynthetic unicellular algae can be cultivated by employing mass production techniques. The harvested Chlorella cells from the mass culturing pools are separated by centrifugation. In the Orient, the pellets are washed and dried in the spray dryer. Finally, the dried powder is packed in vaccum for the starting materials of natural foods. Spray-dried cells of Chlorella were examined by SEM. Most of the droplets of spray-dried cells showed, 50–85μm in diameter (Fig. 1). At the higher magnification, it exhibited that this spherical structure consists of more than a few thousands of single Chlorella cells (Fig. 2), and each cell pilling up or sticking together. The ash-like materials which attached to the surface of cells, probably produced from the cells because of the heat treatment or elevated temperature of hot air from spraying dryers. The cells prepared for SEM by glutaraldehyde fixation and critical point drying had the smooth surface with wrinkled parts. Cells were spherical and measured 2-6 μm in diameter. For the contaminated culture, the photosynthetic purple bacteria are shown to stick on the surface of algal cells. The inside of each particle was revealed by using cryofracture technique. Each particle was occupied by a hole in the center, and its diameter was approximately one-half of the particle in sectional view (Fig. 3).