The Biology of Microalgae - Biotechnological Applications of Microalgae - page 7

2 The Biology of Microalgae
Ranganathan Rajkumar and Zahira Yaakob
Department of Chemical and Process Engineering
University of Kebangsaan, Bangi, Malaysia
CONTENTS
2.1 Taxonomy ......................................................................................................... 7
2.1.1 General Characteristics ........................................................................ 7
2.2 Morphological Identification ............................................................................ 8
2.3 Molecular Identification .................................................................................... 9
2.4 Habitats ........................................................................................................... 12
2.4.1 Freshwater ........................................................................................... 12
2.4.2 Marine................................................................................................. 13
References ................................................................................................................ 14
2.1 TAXONOMY
Algae are a diverse group of organisms that can perform photosynthesis efficiently.
On the basis of morphology and size, algae can be subdivided and are classified
into two main categories: macroalgae and microalgae. Macroalgae consist of mul-
tiple cells that organize into structures resembling the roots, stems, and leaves of
higher plants (e.g., kelp). Microalgae are an extremely diverse group of primary
producers present in almost all ecosystems on Earth, ranging from marine, fresh-
water, desert sands, and hot springs, to snow and ice (Guschina and Harwood,
2006). They are colonial or single-celled organisms that have garnered increasing
amounts of attention and interest for industrial purposes. They are categorized
into divisions based on various characteristics such as morphological features, pig-
mentation, the chemical nature of photosynthetic storage products, and the orga-
nization of photosynthetic membranes. The four most important algal groups in
terms of abundance are green algae (Chlorophyceae), diatoms (Bacillariophyceae),
blue-green algae (Cyanophyceae), and golden algae (Chrysophyceae) (Khan et al.,
2009). According to estimations reported by Cardozo et al. (2007), they include
between 200,000 and 800,000 species, of which about only 35,000 species have
been described.
2.1.1 G eneral C haraCteristiCs
The main characteristics of microalgae are primarily simple morphological features
that can easily be observed under a light microscope. Cyanophyceae consist of prokary-
otic cells commonly called the blue-green algae. They are similar to Gram-negative
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