Production and characterization of titanium dioxide nanoparticles by using bacterial route

In this study, the abilities of 59 bacteria isolated from soil and food samples to produce titanium dioxide nanoparticles were investigated. The best isolate was chosen and nanoparticle production conditions of this isolate were optimized. Characterization, antimicrobial and antioxidant activities of synthesized nanoparticles were analyzed. A total of 32 isolates, that were previously isolated, were used at the begining. It is exposed that some of them were not able to produce titanium dioxide nanoparticles and the others had less amount of production. Besides, 27 isolation was performed from the soil samples collected around Sakarya Maden Deresi and Konya Seydişehir province. According to these isolations and the 16S rDNA gene sequence analysis it was detected that a novel strain, Acinetobacter sp. MDA1 is able to produce titanium dioxide nanoparticles (TiO2NP). For that reason, the study was continued by using this bacterium, encoded MDA1. The effects of pH (6-10), temperature (30-40oC), TiO2 concentration (3,75-20,0 mM) and reaction time (0-144 hours) on the synthesis of NPs were determined. Among the differences made in applications, the formation of TiO2NPs was inspected by observing the change in color from yellow to white by measuring the absorbance at 341 nm using UV-VIS spectrofotometer. According to the spectrofotometric measurements, the best production was achieved in the medium contained 15 mM TiO2 concentration at pH 8 and 33oC in 144 hours. Furthermore, the effects of production conditions on the size of NPs were determined by performing the field emission scaning electron microscopy (FESEM) analysis of NPs. According to the results of analysis, the increase in temperature caused increase in the size of NPs. In addition, it is determined that pH also has effect on the size of NPs and at pH 10 aggregation is occured. X-ray diffractometer (XRD) analysis demonstrated that the NPs possess rutil phase and have spherical shape. The NPs indicated less amount of antimicrobial effect and antioxidant properties are observed.