The Antiviral Activity of Bacterial, Fungal, and Algal Polysaccharides as Bioactive Ingredients: Potential Uses for Enhancing Immune Systems and Preventing Viruses

Abstract

Viral infections may cause serious human diseases. For instance, the recent appearance of the novel virus, SARS-CoV-2, causing COVID-19, has spread globally and is a serious public health concern. The consumption of healthy, proper, functional, and nutrient-rich foods has an important role in enhancing an individual's immune system and preventing viral infections. Several polysaccharides from natural sources such as algae, bacteria, and fungi have been considered as generally recognized as safe (GRAS) by the US Food and Drug Administration. They are safe, low-toxicity, biodegradable, and have biological activities. In this review, the bioactive polysaccharides derived from various microorganisms, including bacteria, fungi, and algae were evaluated. Antiviral mechanisms of these polysaccharides were discussed. Finally, the potential use of microbial and algal polysaccharides as an antiviral and immune boosting strategy was addressed. The microbial polysaccharides exhibited several bioactivities, including antioxidant, anti-inflammatory, antimicrobial, antitumor, and immunomodulatory activities. Some microbes are able to produce sulfated polysaccharides, which are well-known to exert a board spectrum of biological activities, especially antiviral properties. Microbial polysaccharide can inhibit various viruses using different mechanisms. Furthermore, these microbial polysaccharides are also able to modulate immune responses to prevent and/or inhibit virus infections. There are many molecular factors influencing their bioactivities, e.g., functional groups, conformations, compositions, and molecular weight. At this stage of development, microbial polysaccharides will be used as adjuvants, nutrient supplements, and for drug delivery to prevent several virus infections, especially SARS-CoV-2 infection.

Extracellular Polymeric Substances: Still Promising Antivirals

“…Sulfated polysaccharides from the red alga Schizymenia pacifica were also reported to be antiviral against HIV reverse transcriptase and viral replication in vitro [64]. In addition, several polysaccharides from algae, bacteria or fungi, including EPSs produced by lactic acid bacteria (LAB), have been considered as GRAS (generally recognized as safe) by the US FDA, opening interesting possibilities for therapeutics or food supplements [65].…”

“…In general, enveloped viruses are more sensitive to polyanionic antivirals than non-enveloped viruses. On the other hand, in general, the higher the molecular weight, the higher the antiviral activity [59,65,67]. However, although the molecular weight of polysaccharides and EPSs often correlates with their antiviral effect, molecular weight can play a dual role, or even have no influence at all.…”

“…However, some low-molecular-weight polysaccharides can also generate strong antiviral activity, especially when their sulfate content is high; in addition, low-molecular-weight compounds can inhibit cell-to-cell viral spread more efficiently [59]. Low-molecular-weight compounds can inhibit cell-to-cell spread of viruses more efficiently because polysaccharides with low molecular weight can pass more easily through target cells to act inside them [59,65]. In addition, low-molecular-weight EPSs can stimulate the immune system more effectively [41].…”

Health benefits of microalgae and their microbiomes

“…A further interesting fact is that many microalgae communities are able to produce polysaccharides, which are well known to exert a broad spectrum of biological activities, especially antiviral properties (Chaisuwan et al . 2021 ). These polysaccharides were found among numerous algal microbiomes, including S. quadricauda (IMG ID 3300005759), C. saccharophila (IMG ID 3300008885), C. sorokiniana (IMG ID 3300042370) and M. crux‐melitensis (IMG ID 3300008886) (Table 1 ).…”

Targeting Gut Microbiota With Natural Polysaccharides: Effective Interventions Against High-Fat Diet-Induced Metabolic Diseases

“…Natural polysaccharides, one of the most the abundant dietary components, are polymeric carbohydrate macromolecules and sources of fermentable dietary fiber that exhibit biological activities with low toxicity, such as, anti-oxidation, anti-inflammatory, anti-tumor, and antiviral ( Chaisuwan et al, 2021 ; Li et al, 2021a ; Mirzadeh et al, 2021 ). Of note, natural polysaccharides are among the most potent modulators of the gut microbiota composition and benefit for human health ( Yin et al, 2020 ; Song et al, 2021 ).…”