In continuation of our research on the influence of selenium incorporation on the biosynthesis, structure, immunomodulatory and antioxidant activities of polysaccharides of fungal origin, we have isolated from a post-culture medium of Lentinula edodes a selenium (Se)-containing exopolysaccharide fraction composed mainly of a highly branched 1-6-α-mannoprotein of molecular weight 4.5x106 Da, with 15% protein component. The structure of this fraction resembled mannoproteins isolated from yeast and other mushroom cultures, but it was characterized by a significantly higher molecular weight. X-ray absorption fine structure spectral analysis in the near edge region (XANES) suggested that selenium in the Se-exopolysaccharide structure was present mainly at the IV oxidation state. The simulation analysis in the EXAFS region suggested the presence of two oxygen atoms in the region surrounding the selenium. On the grounds of our previous studies, we hypothesized that selenium-enriched exopolysaccharides would possess higher biological activity than the non-Se-enriched reference fraction. To perform structure-activity studies, we conducted the same tests of biological activity as for previously obtained mycelial Se-polyglucans. The Se-enriched exopolysaccharide fraction significantly enhanced cell viability when incubated with normal (human umbilical vein endothelial cells, HUVEC) cells (but this effect was absent for malignant human cervical HeLa cells) and this fraction also protected the cells from oxidative stress conditions. The results of tests on the proliferation of human peripheral blood mononuclear cells suggested a selective immunosuppressive activity, like previously tested Se-polyglucans isolated from L. edodes mycelium. The Se-exopolysaccharide fraction, in concentrations of 10-100 µg/ml, inhibited human T lymphocyte proliferation induced by mitogens, without significant effects on B lymphocytes. As with previously obtained Se-polyglucans, in the currently tested Se-polymannans the selenium content increased the biological activity. However, the activity of selenium exopolysaccharides in all tests was significantly lower than that of previously tested mycelial isolates - most likely due to a different mode of selenium binding and its higher degree of oxidation.

Exopolysaccharides-EPS are long-chain biopolymer with branched, recurring unit of sugars and non-carbohydrate constituents connected to exterior of cells. Rhizobial, a legume nodulating organism is capable of producing EPS. This study investigated the characteristics’ of some Rhizobium EPS and their effects in shelf life extension of some Musa spp. Rhizobial-EPS was produced using yeast extract mineral medium purified by standard methods. The EPS was characterized to determine functional group, thermal stability, chemical compounds and the monosaccharide component using Fourier Transform Infra-red, Spectroscopy, thermogravimetric Analysis (TGA), Gas Chromatography–Mass Spectrometry and HPLC and their bio-preservative property on post-harvest quality of plantain and different banana was done. The Rhizobial-EPS functional groups were hydroxyl, carboxyl, amine, methyl and ethers associated with polysaccharides. Pentadecanoic acid, octadecanoic acid, oleic acid and heptacosanoic acid, and varied concentration of monosaccharides were detected in the exopolysaccharides. The TGA of the EPS shows a constant loss in weight with two quasi-sharp alterations and almost steady plateau. The EPS coated samples had the lowest weight loss across the samples and as such edible coating was effective in delaying weight loss. The weight loss of Musa paradisiaca (plantain) coated with (EPSA obtained from USDA 110), (EPSB USDA 532C) and (EPSC S2) at the first day were 314 and 314.5g. The initial weight loss of coated and uncoated Musa sp. (Apple Banana), Musa acuminata (Lady Finger), and Musa balbisiana (Cooking Banana), ranged from 72 – 72.7g, 96 – 97g and 95 – 98g respectively. The total sugar of EPS Coated Musa sp. ranges from 0.381 – 0.528mg/L, 0.392 – 0.576 mg/L and 0.41 – 0.598 mg/L at days 1, 2 and 3 respectively. The highest Titratable acidity and pH was observed in EPS coated sample. The results obtained from this study proves that EPS solution is a valuable product for fruit preservation and viable for commercial applications.

Biofilm formation is important in the free-living and symbiotic lifestyles of Sinorhizobium meliloti. Here we show that the S. meliloti NspS-MbaA system is homologous to the c-di-GMP modulating NspS-MbaA system described in Vibrio cholerae and modulates biofilm formation, exopolysaccharide (EPS) production and motility in S. meliloti in response to exogenous polyamines. Biofilm and EPS production in quorum sensing-deficient wild type strain 1021 decreased in cultures containing putrescine, 1,3-diaminopropane or spermine, but were unaffected in a 1021 nspS mutant (1021 nspS). Decreases in biofilm formation caused by these polyamines paralleled decreases in EPS production and increases in nspS transcription. Cell aggregation did not differ markedly between strain 1021 and 1021 nspS. The S. meliloti quorum sensing-proficient Rm8530 wild type strain and nspS mutant (Rm8530 nspS) produced similar levels of biofilm under control conditions and 3.2- and 2.2-fold more biofilm in cultures with norspermidine, but these changes did not correlate with EPS production. Rm8530 nspS aggregated up to several fold more than the wild type under most conditions. Changes caused by polyamines in swimming and swarming motility were not generally dependent on NspS-MbaA in either 1021 or Rm8530. We speculate that the S. meliloti NspS-MbaA system could modulate biofilm formation in response to environmental polyamines.

In cystic fibrosis (CF), pulmonary infection with Pseudomonas aeruginosa is a cause of increased morbidity and mortality, especially in patients for whom infection becomes chronic and there is reliance on long-term suppressive therapies. Current antimicrobials, though varied mechanistically and by mode of delivery, are inadequate not only due to eradication failure in many cases, but also because they do not halt the progression of lung function decline over time. One of the reasons for this failure is thought to be the biofilm mode of growth of P. aeruginosa, wherein self-secreted exopolysaccharides (EPSs) provide physical protection against antibiotics and an array of niches with resulting metabolic and phenotypic heterogeneity. Targeting the three EPSs secreted by P. aeruginosa (alginate, Psl and Pel) is currently under investigation as a way of disrupting the biofilm extracellular matrix to potentiate the action of antibiotics. In this review, we look at each EPS as a potential therapeutic target for combatting pulmonary infection with P. aeruginosa in CF, with a particular focus on the current evidence for these emerging therapies and barriers to bringing these therapies into clinic.