Algal biotechnology: An emerging resource with diverse application and potential

Algae include a wide variety of species that range from diatoms, which are microscopic unicellular organisms, to seaweeds extending over 30 m (Fig. 9.1). They constitute a group of approximately 40,000 species, a heterogeneous group that describes a life-form, not a systematic unit; hence, a broad spectrum of phenotypes exists in this grouping. Algae are grouped into six main classes, mainly on the basis of their color (Fogg 1953). Algae are found in fresh or salt water, with a few being terrestrial (e.g., Chrysophyta and Cyanophyta). The eukaryotic algae are placed in the kingdom Protista, classified as euglenoids (phylum Euglenophyta), dinoflage-llates (phylum Pyrrophyta) and diatoms (phylum Bacillariophyta). All have chloro-plasts and carry out photosynthesis similar to that of plants. Prokaryotic blue-green algae belong to the phlyum Cyanobacteria.