Green synthesis, characterization of iron nanoparticles and their use in bioremediation

In this study, the siderophore production capacity of microorganisms isolated from the soil was investigated. The best siderophore-producing microorganism in CAS liquid test was gram (-) bacil and identified as Cronobacter turicensis by 16S rRNA gene sequence analysis. It was observed that the isolated strain called C. turicensis BHC04 has a siderophore with percentage of 65% before optimizing the production conditions. Two different siderophores were investigated since the color changes (orange and purple) at different production hours point to two different siderophores. It was observed that the production of the optimized 1st siderophore increased to 70% in CDLIM medium prepared at OD400, 37 ˚C, 18th hour, pH 8.5, 0 µl FeCl3 concentration, using glycerol as carbon source and ammonium chloride as nitrogen source. On the other hand, the production of the optimized 2nd siderophore increased to 94% in CDLIM medium prepared at 37 ˚C, 28 hours, pH 6.5, 0 µl FeCl3 concentration, using glycerol as carbon source and ammonium chloride as nitrogen source. The study was continued with the second siderophore. After the large-scale production of the siderophore was concentrated by lyophilization, it was purified using Sephadex LH-20 packed column. By evaluating the color and absorbance amounts, 5-20. fractions have been merged. Arnow and Cśaky tests were performed to determine the siderophore type with the purified fractions, and it was found that it contained a high percentage of catecholate type siderophores. For the characterization of the purified siderophore, HPLC, FTIR and 1H-NMR analyzes were performed, respectively, but sufficient data could not be obtained due to the incompatibility with the standards in HPLC analysis and the inability to purify and remove the glycerol used as a carbon source in CDLIM medium in FTIR and 1H-NMR analyzes. Due to the lack of characterization, the study was continued with the Lactobacillus Plantarum BHC03 strain, which was proven to be a catecholate type siderophore by various analyzes in the BAP 2020/108 study. Extracellular biological iron nanoparticle of Fe2O3 was synthesized with the strain supernatant produced under optimum siderophore production conditions. Optimization of the synthesized FeNPs was carried out and it was observed that the optimum conditions were absorbance at OD350, 36 ˚C, 60. and 80. hours, pH 8.5. SEM, EDX, FTIR, XRD and Zeta potential measurement analyzes were performed for the characterization of FeNPs produced at 60th and 80th Hours, respectively. As a result of the characterization, the arsenic removal in water with the 60. hour biological FeNP was investigated, SEM analysis showed that it had a spherical shape with agromes of 80-200 nm in diameter, the presence of iron, oxygen and carbon was proven by EDX, it was observed that it had biological iron nanoparticle spectra with FTIR analysis, and its mean diameter was 86 nm by XRD analysis determined crystal structure, -43.9 mV by Zeta potential measurement analysis. With the ICP analysis, it was observed that the amount of arsenic decreased due to the increase in the amount of biological FeNP. With this thesis, it has been proven that heavy metal (arsenic) in water can be removed with cheaper and environmentally friendly biological iron nanoparticles instead of chemical methods that may cause environmental pollution.