What Is in Store for EPS Microalgae in the Next Decade?

Abstract

Microalgae and their metabolites have been an El Dorado since the turn of the 21st century. Many scientific works and industrial exploitations have thus been set up. These developments have often highlighted the need to intensify the processes for biomass production in photo-autotrophy and exploit all the microalgae value including ExoPolySaccharides (EPS). Indeed, the bottlenecks limiting the development of low value products from microalgae are not only linked to biology but also to biological engineering problems including harvesting, recycling of culture media, photoproduction, and biorefinery. Even respecting the so-called "Biorefinery Concept", few applications had a chance to emerge and survive on the market. Thus, exploiting EPS from microalgae for industrial applications in some low-value markets such as food is probably not a mature proposition considering the competitiveness of polysaccharides from terrestrial plants, macroalgae, and bacteria. However, it does not imply drawing a line on their uses but rather "thinking them" differently. This review provides insights into microalgae, EPS, and their exploitation. Perspectives on issues affecting the future of EPS microalgae are also addressed with a critical point of view.

Keywords: EPS; application; exopolysaccharides; market; microalgae.

Figure 1

Number of references per year between 2000 and 2018 using the key words “polysaccharides and bacteria” (☐) or “polysaccharides and microalgae” (⏹).

Figure 2

Schematic phylogenetic tree representing the distribution of microalgae (colored lineages with representative images) across major eukaryote supergroups. Adapted with permission from Not et al., Advances in Botanical Research, 64, 1–53; published by Elsevier, 2012 [17].

Figure 3

General process strategies to control the production and extraction of exopolysaccharides from microalgae.

Figure 4

Schematic trends of EPS structural features for various microalgae phyla described in the literature over the last decades. The mappings were compiled according to the data published by [7,8], by attributing 0 to 5 averaged points, regarding the richness of each monosaccharide. A1, A2, and A3_1,2 respectively correspond to Haptophytra, Myozozoa, and Ochrophyta. B1, B2, and B3 respectively correspond to Rhodophyta, Charophyta, and Chlorophyta.