Many analyses of gross chemical composition of
different algae have been published in the literature. In
order to give a general overview on the major constituents,
selected data of various micro-algal species are
compiled in Table 1.
Out of the algae listed above, only very few have been
selected finally for large-scale production, i.e. the chlorophyceae
Chlorella sp. and Scenedesmus obliquus and the
cyanobacteria Spirulina sp. and Athrospira sp. Chlorella is
a spherical, eukaryotic, unicellular alga with a diameter of
5–10 μm. Its hemicellulotic cell wall accounts for the
rigidity of the cells. The green alga Scenedesmus is of
similar size but forms 4-celled colonies. Spirulina and
Arthrospira are photosynthetic, filamentous, spiral-shaped,
multi-cellular organisms attaining sizes of 0.5 mm in
length. They were classified formerly to the blue-green
algae, however, due to their prokaryotic structure they
nowadays belong to the cyanobacteria.