Microalgae are used in flocculation processes because biopolymers are released into the culture medium. Microalgal cell growth under specific conditions (temperature, pH, luminosity, nutrients, and salinity) provides the production and release of exopolysaccharides (EPS). These biopolymers can be recovered from the medium for application as bioflocculants or used directly in cultivation as microalgae autoflocculants. The optimization of nutritional parameters, the control of process conditions, and the possibility of scaling up allow the production and industrial application of microalgal EPS. Therefore, this review addresses the potential use of EPS produced by microalgae in bioflocculation. The recovery, determination, and quantification techniques for these biopolymers are also addressed. Moreover, other technological applications of EPS are highlighted.

Keywords: arabinose; proteins; Spirulina; Synechococcus; xylose

The scarcity of oil resources, the pollution generated by agro-food wastes, and the inadequate disposal of petrochemical polymers have been issues of great concern in recent years. In this way, research has driven the search for the use of these wastes and the production of renewable and biodegradable materials such as biopolymers. In this sense, microalgal biotechnology emerges as a strategy to minimize these problems, since these micro-organisms can use agro-food wastes to produce biomass rich in bio compounds such as biopolymers. Among the biopolymers synthesized by microalgae, polyhydroxybutyrate (PHB) has been widely studied, mainly because it has properties similar to polymers of fossil origin. Besides, the production of PHB by microalgae can be applied to improve the economic viability of the commercialization of this polymer by using alternative sources of nutrients in integrated biorefinery systems. Thus, while it performs the remediation of residues, microalgae produce compounds with high added value, contributing to promoting the industrial-scale production of PHB, which expands the prospects for the application of biopolymer in several areas. Therefore, this chapter addresses the environmental impacts caused by agri-food wastes and the potential use of these alternative nutritional sources to produce PHB by microalgae. The PHB synthesis process and the economic prospects for the production of PHB of microalgal origin are also presented.