There are 3 varieties of Chlorella
Chlorella is a unicellular eukaryotic alga that grows under both phototrophic and mixotrophic conditions mainly in freshwater. Botanists describe a large number of species of Chlorella but today recognize only three varieties (Krienitz et al., 2004) .
The three varieties of Chlorella defined by botanists are:
• Chlorella vulgaris
• Chlorella lobophora
• Chlorella sorokiniana
The taxonomic criterion for the determination of the genus Chlorella was established by Fott et al. 1969 . Chlorella vulgaris is nowadays the most cultivated chlorella, especially for the production of organic Chlorella. This variety has proven to be particularly suitable for cultivation in microalgae farms. Chlorella vulgaris, which, until a few years ago, was attached to the taxon Chlorella pyrenoidosa, shows an extremely fast growth both in phototrophic and mixotrophic conditions when maintained in favorable culture conditions.
The taxon Chlorella pyrenoidosa is now extinct (Kessler 1976, 1992) [3,4].According to the classification of taxa, Chlorella are chlorophytes, so-called green algae.
The organisms called Chlorellaceae belong to the chlorophytes (green algae) to the group Trebouxiophyceae. The Chlorellaceae are divided into two related groups, the parachlorella group and the chlorella group, of which Chlorella vulgaris is a member (Krienitz et al., 2004) . They are cocciated green algae that have small spherical green cells, often referred to as “green balls”.
To distinguish the species from each other, different characteristics are always studied: e.g. ultrastructure of the cell wall, ultrastructure of the pyrenoids, chemical composition of the cell wall, serological cross-reactions, physiology, biochemistry, morphology and molecular biology.
The species “Chlorella pyrenoidosa” would not exist!
Chlorella pyrenoidosa would be a mixture of species composed in majority of vulgaris.
In 1992 various deposits of algal cultures named “Chlorella pyrenoidosa” were examined, showing that the cultures named Chlorella pyrenoidosa should be classified in different species. It was possible to identify strains of Chlorella vulgaris that had been wrongly deposited under the name “Chlorella pyrenoidosa”.A large part of the algal cultures classified as “Chlorella pyrenoidosa” belong in fact to the species Chlorella sorokiniana. Chlorella fusca” is no longer classified in the genus Chlorella but in the related genus Scenedesmus (Kessler & Huss; 1992) .
By 1999, three species and Chlorella kessleri were included in the genus Chlorella (Huss et al., 1999) .Thus, today, only three species constitute the Chlorella group: Chlorella vulgaris, Chlorella lobophora and Chlorella sorokiniana (Krienitz et al., 2004).
The classification and differentiation of chlorella is difficult and remains a matter for specialists. They are species with most of their characteristics very similar. Of course, this complicates determination and classification, resulting in misclassification and duplication. More than 100 species of Chlorella have been described, most of which had to be revised.
See the communication of 10/04/2014 of the CENTRE D’ETUDE ET DE VALORISATION DES ALGUES : CEVA “Chlorella pyrenoidosa : une espèce mal nommée” .