Section 5 Microalgae Biomass

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bacteria [1, 2].

**Chapter 19**

**Abstract**

**1. Introduction**

Microalgae: The Multifaceted

Microalgae are unicellular, eukaryotic organisms which possess unique qualities

**Keywords:** biomass production, autotrophy, heterotrophy, mixotrophy, wastewater

Algae represent a highly diverse consortium of polyphyletic, thallophytic, photosynthetic, and cryptogamic organisms. *They* are morphologically simple, chlorophyll-containing, non-flowering, and typically aquatic plants of a large family with members including seaweeds and a range of microscopic and unicellular to very large multicellular organisms [1]. Algae are either prokaryotes or eukaryotes and lack vascular tissue, leaves, true stems, and roots. The prokaryotic algae are the blue-green algae, which are also referred to as Cyanobacteria or Cyanoprokaryota and belong to the kingdom Eubacteria. The eukaryotic algae belong to the kingdom Protoctista. Cyanobacteria also derive their energy through photosynthesis but do not have a nucleus and membrane-bound organelles, like chloroplasts (see **Figures 1** and **2**) and their prokaryotic nature describes the single-stranded deoxyribonucleic acid (DNA) in their formation, which confers the bacterial identity. On the other hand, eukaryotic algae have double-stranded DNA in their makeup and are equipped with a nucleus and chloroplast. The term "algae" is therefore exclusively reserved for the eukaryotic organisms; and this chapter considers and treats the prokaryotic cyanobacteria as

treatment, pollutant sequestration, microalgal lipid production, biofuels,

of replication, producing biomass as a precursor for biofuels, nutraceuticals, biofertilizer, and fine chemicals including hydrocarbons. Microalgae access nitrates and phosphates in wastewater from municipalities, industries, and agricultural processes to grow. Wastewater is, therefore, culture media for microalgae, and provides the needed nutrients, micronutrients, inorganic and organic pollutants to produce microalgae biomass. Suitable strains of microalgae cultivated under mesophilic conditions in wastewater with optimized hydrodynamics, hydraulic retention time (HRT), luminous intensity, and other co-factors produce biomass of high specific growth rate, high productivity, and with high density. The hydrodynamics are determined using a range of bioreactors from raceway ponds, photobioreactors to hybrid reactors. Carbon dioxide is used in the photosynthetic process, which offers different growth stimuli in the daytime and the night-time as the microalgae cultivation technique is navigated between autotrophy, heterotrophy, and mixotrophy

Biomass of the 21st Century

*Donald Tyoker Kukwa and Maggie Chetty*

resulting in microalgal lipids of different compositions.

nutraceuticals, biofertilizer, photobioreactors, hybrid reactors
