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.

Bioactive Polysaccharides from Seaweeds

“…Seaweeds are known as producers of various biologically active macromolecules (polyphenols, diterpenes, fiber, proteins and notably polysaccharides) with different structural and physicochemical properties and interesting functional characteristics. Regarding the production of these bioactive substances, algae are considered the most abundant source of polysaccharides, which may be sulfated (fucoidans, carrageenans, galactans, and agars) and non-sulfated (alginates, laminaran) [ 6 ]. These high molar mass biopolymers (10 to 1000 kDa) have extremely varied structures and are mainly made up of osidic unit sequences (pentoses and/or hexoses) linked by O -glycosidic bonds.…”

“…The monosaccharide sequences can consist of neutral ones (e.g., Glc, Gal, Xyl, Fuc, Ara, Man), acidic ones (GlcA, GalA, etc.) or hexosamines (GlcNAc, GalNAc) [ 1 , 6 ]. It was reported that these polymers can be linear (alginates, cellulose), but also branched (fucoidans, sulfated galactans).…”

Natural freshwater microalgae biofilm as a tool for the clean-up of water resulting from mining activities

“…This principle tends to be insignificant for natural freshwater biofilm formation because at the early growth stage, the biofilm is not yet settled based on its low density and absence of EPS, thereby using up lesser amount of nutrients compared to that at the late growth stage when the microalgae is fully matured, which has higher density and settle comfortably on the organic substrate (Zhu et al 2016). The formation of EPS also contributes to the high usability of nutrient because the EPS aids the attachment of other non-microalgae organism which also need nutrient to survive (Pierre et al 2019). Studies have shown that elevated nutrients concentration in aquatic environment tends to promote EPS production while nutrient starvation leads to the degradation of EPS resulting to the detachment of the contributing organism in the biofilm formation (Kesaano and Sims 2014).…”

“…Natural freshwater biofilm depends on light for formation, because freshwater microalgae are autotrophic organisms that rely on light for the production of food via photosynthesis and also EPS production (Pierre et al 2019). The availability and duration of light tend to play a significant role in the formation of freshwater microalgae biofilm in natural environment (Shen 2014).…”

The Follow-up Photobioreactor Illumination System for the Cultivation of Photosynthetic Microorganisms

“…In the case of excessive intensity of lighting, the known solutions are used to inhibit the growth of biomass, which directly translates into the result of productivity. In the above systems it is also difficult to control temperature or gas removal [24,25]. There is also an example of a Polish photobioreactor solution contained in patent specification PL 224183 regarding a flat panel intended for growing microorganisms in the natural environment.…”