Résumé : INTRODUCTION Exopolysaccharides (EPSs) are high-value functional biomaterials mainly produced by bacteria and fungi, with nutraceutical, therapeutic and industrial potentials.1 Fungal EPSs can be produced within a few days, using simple recovery approaches and by utilizing industrial waste as feedstock.2, 3In this study, EPSs from three fungal strains, Papiliotrema terrestris PT22AV, Rhodosporidium babjevae IBRC-M 30088 and Sclerotium glucanicum DSM 2159 were extracted and their physicochemical properties (structural, morphological, monosaccharide composition and thermal properties) were characterized. Also, in vitro biological activities as well as wound healing potential of the EPSs was evaluated.EXPERIMENTAL METHODSMicroorganism cultivation P. terrestris PT22AV, a yeast isolated from olives in Molise (Italy), R. babjevae and S. glucanicum were cultured in agar media. After preparation of appropriate inoculum for each strain, batch cultures consisting of 250 mL Erlenmeyer flasks containing 100 mL medium were used for microbial growth and production of EPSs. EPS extraction and purification After incubation, the EPS-containing supernatants were recovered via centrifugation and the EPSs were precipitated by adding cold ethanol, purified by dialysis, and lyophilized. Morphological and physicochemical characterization of the extracted EPSs Scanning electron microscopy (SEM) observations were performed for microstructure determination of the EPSs from P. terrestris and S. glucanicum. Also, FT-IR analyses were done for functional group determination of the EPSs.SEM and FT-IR studies had been done previously for R. babjevae. Molecular weight (Mw) determination [through steric exclusion chromatography (SEC)-HPLC1)] and monosaccharide composition determination (GC-MS), were performed for the EPSs from P. terrestris. For the other two strains, Mw and monosaccharide composition is already available. In vitro biological activity The antioxidant activity of the EPSs was assessed by measuring their DPPH radical scavenging activity. Also, their compatibility with human red blood cells (RBCs) and human fibroblasts (ATCC: CCL-186) and macrophages (U937, ATCC: CRL-1593.2) cell lines was assessed.In vivo wound healing studies The wound healing effects of the three EPSs were evaluated in vivo using adult male Wistar rats based on wound closure percentage (WC)% and histopathological assessments. Statistical analysis Minitab ®20.4 software was used to conduct statistical analysis of the WC% association with various time intervals and treatment groups. GraphPad Prism 9.0.0 (GraphPad Software, LLC, USA) was used for in vitro data analysis. Since data of WC% and cell viability followed a non-parametric distribution, the two-way ANOVA test with Dunnett's multiple comparisons was used. Statistical significance was considered at p < 0.05.RESULTS AND DISCUSSION The EPSs obtained from P. terrestris had an average molecular weight of 202 kDa. Mannose and glucose with 97% and 3% molar percentages, respectively, constituted the EPSs which was then considered as mannan polysaccharides. SEM showed that this EPSs have porous surface structure with grain-like elongated structural units. The antioxidant activity of the EPS at different concentrations (0.1-5 mg/mL) showed a positive correlation between the EPS concentration and the DPPH radical antioxidant activity. The increase of EPSs concentration from 0.1 mg/mL to 5 mg/mL, improved the scavenging activity from 20 % to 37 %. Scleroglucan (the EPSs from S. glucanicum) was also shown to have a solid surface characterized by irregular shapes. IR spectroscopy indicated the presence of hydroxyl, carbonyl, and carboxyl functional groups like the commercial scleroglucan. DPPH scavenging activity of scleroglucan was 33.03 ± 4.31% at a concentration of 5 mg/mL. All the three EPSs showed compatibility with the human fibroblast and macrophage cell lines (at concentrations of 100-1000 µg/mL), and with RBCs (1-10 mg/mL). The animal studies showed a dose-dependent wound healing capacity of three EPSs with significantly higher WC% values at 10 mg/mL after 14 days. The effects of the three EPSs on WC% were not significantly different at the highest concentration (10 mg/mL).CONCLUSIONS These findings demonstrate that the EPSs from P. terrestris, R. babjevae and S. glucanicum are promising biopolymers for wound healing acceleration. REFERENCES1. Vinothini G, et al. Int. J. Biol. Macromol. 134:575-87, 20192. Elsehemy IA, et al. Int J Biol Macromol. 163:1196-207, 20203. Donot F, et al. Microbial exopolysaccharides: Main examples of synthesis, excretion, genetics and extraction. Carbohydr Polym. 87:951-62, 2012