Biosynthesis of Zinc Oxide (ZnO) Using Culture Biomass of Aspergillus Niger : The Influence of pH On Textile Morphology And Antimicrobial Activity

Abstract

The biosynthesis of zinc oxide (ZnO) is performed through enzymatic mechanisms, by controlling the particle size and morphology of the compound using the sol-gel method. Furthermore, this method utilizes stabilizer obtained from the cell biomass of Aspergillus niger bacteria, in order to yield homogeneous and consistent products, which corresponds with the XRD outcome that exhibits good crystallinity. The evaluation of functional, morphological, and antibacterial activities was carried out at pH 6.0-13.0, as the prepared samples were characterized by FT-IR. The analysis showed the interaction of hydroxyl groups, aromatic rings, as well as N-H and O-Zn-O compounds at a wavenumber of 401-584 cm−1. The XRD and SEM characterizations showed that the structure and crystal phase of ZnO were hexagonal wurtzite at dimensions of 36.2 - 45.4 nm. The differences in pH also influenced the dimensions, morphology, and antimicrobial activity. ZnO with pH of 8.0 was characterized by FESEM-EDAX, based on the analysis of morphological uniformity. This characterization obtained rod and cube structures, with atomic ratios of Zn = 61.5% and O = 38.5%. The UV-DRS spectrum showed that the optical band gap was not significantly influenced by the pH of the reactant solution, with a value of Eg = 3.00–3.11 eV. The differences in morphology further distinguished anti-bacterial properties on textile fibres, through the use of the Gram-negative and positive bacteria (Pseudomonas aeruginosa and Staphylococcus aureus), with inhibition zones of 17-21 mm and 21-25 mm, respectively. Therefore, ZnO is classified as a very strong antibacterial material compared to amoxicillin, with an inhibition zone of 13.6 mm.