Extracellular Polymeric Substances Produced by the Thermophilic Cyanobacterium Gloeocapsa gelatinosa: Characterization and Assessment of Their Antioxidant and Metal-Chelating Activities

Abstract

Cyanobacteria, particularly thermophilic strains, represent an important potential source of EPSs, harboring structural complexity that predicts diverse and specific bioactive potential. The thermophilic cyanobacteria Gloeocapsa gelatinosa, isolated from a natural hot source in Ain Echfa (Tunisia), was cultivated in a cylindrical reactor, and the production of biomass and EPSs was investigated. Results revealed that the strain is amongst the most efficient EPSs producers (0.89 g L−1) and that EPSs production was not correlated with the growth phase. EPSs were sulfated heteropolysaccharides containing carbohydrates (70%) based on nine different monosaccharides, mainly mannose (22%), and with the presence of two uronic acids. EPSs were formed by two polymers moieties with a molecular weight of 598.3 ± 7.2 and 67.2 ± 4.4 kDa. They are thermostable in temperatures exceeding 100 °C and have an anionic nature (zeta potential of −40 ± 2 mV). Atomic force microscopy showed that EPSs formed multimodal lumps with 88 nm maximum height. EPSs presented high water holding capacity (70.29 ± 2.36%) and solubility index (97.43 ± 1.24%), and a strong bivalent metal sorption capacity especially for Cu2+ (91.20 ± 1.25%) and Fe2+ (75.51 ± 0.71%). The antioxidant activity of G. gelatinosa EPSs was investigated using four methods: the β-carotene-bleaching activity, DPPH assays, iron-reducing activity, and metal-chelating activity. EPS has shown high potential as free radicals’ scavenger, with an IC50 on DPPH (0.2 g L−1) three-fold lower than ascorbic acid (0.6 g L −1) and as a metal chelating activity (IC50 = 0.4 g L−1) significantly lower than EDTA. The obtained results allow further exploration of the thermophilic G. gelatinosa for several biotechnological and industrial applications.

Optimization and Characterization of a Novel Exopolysaccharide from Bacillus haynesii CamB6 for Food Applications

“…The in vitro antioxidant activity shows prodigious potentiality to be developed as an antioxidant agent, as well as a functional additive for the food industry. A similar study was previously undertaken by Gongi et al [ 82 ], in which thermophilic Gloeocapsa gelatinosa showed similar results. Thus, EPS with an improved antioxidant capacity is reported to be utilized as antioxidant food additives [ 2 ].…”

Photocatalytic Dye Degradation Potential of Silver Nanocomposite from Exo-polysaccharide of Bacillus sp., An Associative Bacterium of Sargassum wightii

“…The maximum absorption spectral wavelength area was found between 200 -230 nm, which exhibits its characteristics of functional group such as ester, carbonyl, carboxyl, and amine (Figure 2). The results are in coincidence with previous studies of marine cyanobacterium, Gloeocapsa gelatinosa (20) .…”

“…FTIR spectra of the crude EPS produced by Bacillus sp. showed two O-H stretching at 3745 cm -1 and 3274 cm -1 (3200 -3800 cm -1 range) and are the typical characteristic of a carbohydrate group similar to Gloeocapsa gelatinosa (20) . A weak Chttps://www.indjst.org/ H stretching band was absorbed in 2931 cm -1 can be attributed to the C-H stretching of methyl groups, which are typically found in hexoses such as glucose or galactose or deoxyhexoses such as rhamnose or fucose in reference to previous studies by Bacillus xiamensis (18) .…”

Microbial Polysaccharides Extracted from Different Mature Muds of the Euganean Thermal District Show Similar Anti-Inflammatory Activity In Vivo

“…The results obtained agree with several studies that showed that polysaccharides with a net negative charge ameliorates their water solubility and activity as an ion exchange matrix of cations. In particular, polysaccharides that contains the functional groups and the characteristics mentioned above are able to reduce redox potential, stabilise the oxidation form of metal ions, prevent the production of excessive free radicals and protect the body from oxidative stress by chelating metal ions [31,32]. The analysis of monosaccharide composition of lyophilized samples revealed the presence of 11 different monosaccharide moieties, including two uronic acids and two amino sugars, as shown in Figure 4.…”