Production and characterization of exopolysaccharide from thermophilic bacteria

Objective: In this thesis, it was aimed to examine the exopolysaccharide (EPS) production of thermophilic bacterial isolates, to purify and biological characterization of EPS produced by the productive isolates. In addition, the detailed chemical analysis of EPS produced by the HBB 111 thermophilic bacterial isolate, which was selected for the best production, and the optimization of the production conditions constituted the other objectives of the thesis. Materials and Methods: In this doctoral thesis study, EPS extraction and phenol sulfuric acid method were used to determine the exopolysaccharide production of thermophilic bacteria that were previously isolated from hot water sources in Aydın and its surroundings. Cytotoxicity by hemolytic potential test of ten thermophilic EPSs was analyzed by agar well diffusion method and spectrophotometrically in 96 microplate. Its antimicrobial activity was investigated by agar-well diffusion method. Antioxidant capacities and inhibition of alpha-amylase enzyme were examined spectrophotometrically with a 1mL cuvette. Prebiotic activities were investigated by cell counting method. Fibrinolytic activity was investigated by modifying the USP 28-NF 23 pharmacopeia (2005) method. For the antibiofilm capacities, staining method with crystal violet on 96 microplate was used. HBB 111 isolate was selected among ten EPS producers and TLC, FTIR-ATR, NMR, GC-MS and SEM-EDX chemical analyzes of the EPS produced were performed. Time, temperature, pH, NaCl concentration, sugar type and sugar concentration parameters were tested in the optimization of EPS production conditions. Results: In this thesis study, it was determined that EPSs produced by ten thermophilic isolates have anti-cytotoxicity, antimicrobial, antioxidant, alpha-amylase enzyme inhibition, prebiotic, fibrinolytic and antibiofilm activities. It was determined that the exopolysaccharide EPS111, which was chosen because it was more efficient in the study, was positive in terms of all biological activities tested. Additionally, according to TLC, FTIR-ATR, NMR, GC-MS, and SEM-EDX analysis results, EPS 111 was determined to be a heteropolysaccharide containing glucose, galactose and fructose monosaccharides, with a rough and layered surface. Optimum production conditions were determined as 26 hours of incubation, 55 °C, pH 8.0, media free of NaCl, and media containing 2.4% lactose. Conclusion: In recent years, EPSs produced by extremophilic bacteria stand out with their potential for use in health, food and cosmetics industries. In this thesis study, it is thought that EPS produced by HBB 111 can be used in food areas, due to the antioxidant, anticytotoxic and prebiotic properties and in health areas due to its anticytotoxic, antimicrobial, antibiofilm, alpha amylase inhibition, prebiotic, and fibrinolytic properties. Unlike thermophilic EPSs reported in the literature, EPS 111 appears to have multiple biological activities. Key Words: Thermophilic Bacteria, Exopolysaccharide, Biological Activity, Chemical Characterization.