Potential functions and applications of diverse microbial exopolysaccharides in marine environments

Abstract

Exopolysaccharides (EPSs) from microorganisms are essential harmless natural biopolymers used in applications including medications, nutraceuticals and functional foods, cosmetics, and insecticides. Several microbes can synthesize and excrete EPSs with chemical properties and structures that make them suitable for several important applications. Microbes secrete EPSs outside their cell walls, as slime or as a "jelly" into the extracellular medium. These EPS-producing microbes are ubiquitous and can be isolated from aquatic and terrestrial environments, such as freshwater, marine water, wastewater, and soils. They have also been isolated from extreme niches like hot springs, cold waters, halophilic environments, and salt marshes. Recently, microbial EPSs have attracted interest for their applications such as environmental bio-flocculants because they are degradable and nontoxic. However, further efforts are required for the cost-effective and industrial-scale commercial production of microbial EPSs. This review focuses on the exopolysaccharides obtained from several extremophilic microorganisms, their synthesis, and manufacturing optimization for better cost and productivity. We also explored their role and applications in interactions between several organisms.

Keywords: Antifouling agents; Bioremediation; Marine environment; Microbial exopolysaccharides.

Fig. 1

Biofilm production by H. japonica T5 [31]

Fig. 2

Mucoid colony of an exopolysaccharide-producing microbe on solid media [34]

Fig. 3

The structure of a “sheath” of the unicellular Chroococcus sp. [71]

Fig. 4

The exopolysaccharides of Cyanospira capsulata [22]

Fig. 5

The general steps for production, extraction, and characterization of exopolysaccharides

Fig. 6

General steps involved during the formation of the exopolysaccharide matrix of a biofilm

Fig. 7

Aggregation of organic carbon by exopolysaccharides and scavenge some metal ions then sink to the bottom [108]