The aim of this study was to monitor the influence of the fermentation conditions on the exopolysaccharides (EPS) biosynthesis. For this, different culture media compositions were tested on an isolated lactic acid bacteria (LAB) strain, identified by 16S rDNA sequence as being Weissella confusa. It was proved that this bacterial strain culture in MRS medium supplemented with 80g/L sucrose and dissolved in UHT milk produced up to 25.2g/L of freeze-dried EPS, in static conditions, after 48h of fermentative process. Using FTIR and NMR analysis, it was demonstrated that the obtained EPS is a dextran. The thermal analysis revealed a dextran structure with high purity while GPC analysis depicted more fractions, which is normal for a biological obtained polymer. A concentration up to 3mg/mL of dextran proved to have no cytotoxic effect on normal human dermal fibroblasts (NHDF). Moreover, at this concentration, dextran breaks up to 70% of the biofilms formed by the Candida albicans SC5314 strain, and has no antimicrobial activity against standard bacterial strains. Due to their characteristics, these EPS are suitable as hydrophilic matrix for controlled release of drugs in pharmaceutical industry.
Keywords: 16S rDNA; Cytotoxicity; Exopolysaccharide; GPC; NMR; UHT milk.
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