2.3. Bacteria-Mediated Biogenic Synthesis of TiO2 Nanoparticles

In contrast to other kinds of microorganisms, bacteria were utilized to synthesize nanoparticles earlier. Due to the mild conditions, high yield, and easy purification and manipulation, bacteria become the most widely studied microorganism, with the title of “the factory of nanomaterials” [42]. Previously, different researchers made use of bacteria as a reducing and a capping agent to control the grain/overgrowth during the synthesis of titanium dioxide nanoparticles and other nanomaterials having various applications [42]. TiO₂ NPs were synthesized in the presence of Aeromonas hydrophila bacteria using the bulk form of TiO₂ as a precursor. The XRD pattern of the synthesized TiO₂ NPs estimated the size as 40.50 nm having spherical morphology as it was confirmed from FESEM analysis [43]. Moreover, a research report show that TiO₂ NPs were synthesized in the presence of Planomicrobium spp. bacteria using the bulk form of TiO₂ as a precursor [44, 45]. The XRD crystal size of the obtained TiO2 NPs measured was 8.89 nm. In addition, TiO₂ NPs were synthesized using the bacteria Bacillus mycoides in the presence of titanyl hydroxide as the precursor. The obtained TiO₂ NPs produced were predominately anatase crystal with a polydisperse size of 40–60 nm [46]. Advantages of using a bacterial system include easy handling and hereditary manipulation without much difficulty. As it was stated by different scholars, bacteria have been employed in commercial biotechnological processes such as bioleaching and bioremediation. Bacteria possess remarkable abilities to reduce heavy metal ions and are potential candidates for TiO₂ nanoparticles synthesis [42, 47].