Extracellular polymeric substance
Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by microorganisms into their environment.
EPSs are the construction material of bacterial settlements and either remain attached to the cell's outer surface, or are secreted into its growth medium.
[12] Currently, exopolysaccharides have received much attention for their antibacterial, anti-oxidative, and anticancer properties, which lead to the development of promising pharmaceutical candidates.
They provide structural integrity to biofilm matrix and act as a scaffold to protect bacterial cells from shear forces and antimicrobial chemicals.
[19] Most EPS from cyanobacteria are also complex anionic heteropolymers containing six to ten different monosaccharides, one or more uronic acids, and various functional substituents such as methyl, acetate, pyruvate, sulfate groups, and proteins.
It is speculated that the release of complex mixtures of macromolecular polyelectrolytes with high polysaccharide content contributes to the survival strategy of D. salina in varying salt concentrations.
These enzymes are crucial for breaking down large molecules in the environment into smaller ones that the microorganisms can absorb (transport into their cells) and use for growth and energy.
These inhibitors are crucial in various biological processes and therapeutic applications, as proteases play key roles in numerous physiological functions, including digestion, immune response, blood coagulation, and cell signaling.
[49] Studies on P. aeruginosa, B. subtilis, V. cholerae, and S. mutans suggested that the transition from initial cell clustering to microcolony appears to be conserved among different biofilm-forming model organisms.
[49] As an example, S. mutans produces an exoenzymes, called glucosyltransferases (Gtfs), which synthesize glucans in situ using host diet sugars as substrates.
Replication of early colonizers will be facilitated by the presence of organic molecules in the matrix which will provide nutrients to the algal cells.
Several factors contribute to the composition of EPS including species, substrate type, nutrient availability, temperature, pH and light intensity.
[59] Exopolysaccharides can facilitate the attachment of nitrogen-fixing bacteria to plant roots and soil particles, which mediates a symbiotic relationship.
[61] The binding affinity and metal specificity of EPSs varies, depending on polymer composition as well as factors such as concentration and pH.
[62] There is evidence that the adhesion and metal-binding ability of EPS affects mineral leaching rates in both environmental and industrial contexts.
[65] The physical and chemical characteristics of bacterial cells can be affected by EPS composition, influencing factors such as cellular recognition, aggregation, and adhesion in their natural environments.
[65] So far, biomass-based production of industrial microalgae has been widely applied in the fields from food and feed to high-value chemicals for pharmaceutical and ecological applications.
Therefore the application of recycling methods motivated by the simultaneous generation of high value products from spent medium bears potential in commercial and environmental perspectives.
[29] In nutraceutical industries, Arthrospira (Spirulina) and Chlorella are the most important species in commercialization as health foods and nutrition supplements with various health benefits including enhancing immune system activity, anti-tumor effects, and animal growth promotion, due to their abundant proteins, vitamins, active polysaccharides, and other important compounds.
[73] For instance, adenosine from Phaeodactylum tricornutum, can act as an anti-arrhythmic agent for the treatment of tachycardia and the green algal metabolite caulerpin is featured in studies of anti-tuberculos is activities.
[74][75] Moreover, some extracellular polysaccharides from microalgae have various bioactivities involving antitumor, anti-inflammatory, and antiviral activity, providing promising prospects for pharmaceutical applications.
[81] B. subtilis has gained interest for its probiotic properties due to its biofilm which allows it to effectively maintain a favorable microenvironment in the gastrointestinal tract.
[82] Production of oleaginous microalgae are becoming attractive as alternative sources of biofuels with potential to meet global demand for renewable bioenergy.
For instance, marine microalgae release a large amount of dissolved organic substances (DOS), which serve as energy sources for heterotrophs in algal-bacterial symbiotic interactions.
[89] In B. subtilis, the protein matrix component, TasA, and the exopolysaccharide have both been shown to be essential for effective plant-root colonization in Arabidopsis and tomato plants.
[90] Due to the growing need to find a more efficient and environmentally friendly alternative to conventional waste removal methods, industries are paying more attention to the function of bacteria and their EPS sugars in bioremediation.
[91] Researchers found that adding EPS sugars from cyanobacteria to wastewaters removes heavy metals such as copper, cadmium and lead.
[91] Some contaminated soils contain high levels of polycyclic aromatic hydrocarbons (PAHs); EPSs from the bacterium Zoogloea sp.
[3] "smart release" nanocarriers that can penetrate biofilms and be triggered by pathogenic microenvironments to deliver drugs or multifunctional compounds, such as catalytic nanoparticles to aptamers, dendrimers, and bioactive peptides) have been developed to disrupt the EPS and the viability or metabolic activity of the embedded bacteria.
[18] This article incorporates text by Lu Liu, Georg Pohnert, and Dong Wei available under the CC BY 4.0 license.
