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

Marine Drugs

Juan Luis Gomez Pinchetti¹  Nereida Cordeiro²  Hatem Ben Ouada³  Wejdene Gongi³ 

[1] Banco Español de Algas (BEA), Instituto de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Muelle de Taliarte s/n, 35214 Telde, Spain;LB3-Faculty of Science and Engineering, University of Madeira, 9020-105 Funchal, Portugal;Laboratory of Blue Biotechnology & Aquatic Bioproducts, National Institute of Marine Sciences and Technologies, Monastir 5000, Tunisia;

关键词: Gloeocapsa gelatinosa;    extracellular polymeric substances;    physicochemical characterization;    functional properties;    antioxidant activity;    extremophilic;   

DOI  :  10.3390/md20040227

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown