Investigation of Exopolysaccharide (EPS) production potential in Euhalothece sp. AQUAMEB-3 strain and the biotechnological applications of the obtained EPS

This thesis investigates the species identification of the AQUAMEB-3 cyanobacteria strain isolated from İzmir Çamaltı Saltern, characterizes the exopolysaccharides (EPS) produced by the cyanobacteria for potential biotechnological uses, and investigates their use in wound dressing applications. Phylogenetic study of the 16S rRNA gene sequence indicated that the AQUAMEB-3 strain, exhibiting varying morphologies in response to environmental conditions, is suitably categorized as Euhalothece sp. AQUAMEB-3. The Euhalothece sp. AQUAMEB-3 strain produced 0.89 ± 0.15 g L-1 of exopolysaccharide during the stationary phase, with the composition containing 267.8 ± 76.0 mg g-1 carbohydrate, 70.6 ± 4.8 mg g-1 neutral sugar, 90.8 ± 34.9 mg g-1 uronic acid, and 42.6 ± 16.0 mg g-1 protein. The structural characterisations of the porous EPS revealed the presence of carboxyl, hydroxyl, amine, and sulfate groups. The melting point of the synthesized EPS was 86.6 °C, exhibiting thermal stability up to 243.4 °C and keeping its thermostability up to 347.5 °C. Euhalotece sp. AQUAMEB-3 EPS solution exhibited significant emulsification properties comparable to commercial xanthan gum, with an emulsification index (E24) of 94.2 ± 3.2%. Euhalothece sp. AQUAMEB -3 EPS exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli, with minimum inhibitory concentration (MIC) values of 300 ppm and 150 ppm, respectively. EPS exhibited 82.6 ± 25.8% radical scavenging activity at a dose of approximately 9 mg mL-1, indicating its antioxidant capabilities. Subsequently, hydrogel wound dressings were formulated with PVA using various ratios of EPS The analytical results of the produced wound dressings indicated that the optimal hydrogel formulation comprised 1% EPS, 5% PVA, and 1% glutaraldehyde. The swelling ratios of the synthesized EPS-based hydrogel film were a maximum of 546.9 ± 72.9% and 325.7 ± 55.6% at equilibrium. The results indicated that the hydrogel exhibited a degradation of 54.8 ± 4.06% after 14 days, a degradation temperature of 127 °C, a water vapor permeability rate of 2094.85 ± 590.92 gr m²/24, and demonstrated antioxidant, biocompatible and antibacterial, properties against Escherichia coli and Staphylococcus aureus bacteria.