Biofabrication of TiO2 nanoparticles via Aspergillus niger DS22 supernatant: bioreactor optimization and multi-activity profiling

Abstract

AbstractThe study presents a safe and eco-friendly green synthesis of titanium dioxide nanoparticles (TiO2 NPs) using Aspergillus niger DS22 (ON076463.1) cell-free filtrate, focusing on optimizing factors affecting nitrate reductase enzyme production within the framework TiO2 NP biosynthesis. Maximum enzyme activity was accomplished by growing A. niger DS22 in a modified MYGP medium at pH 6, 0.5% peptone, 0.15% yeast extract, 0.25% KNO3, 2% glucose, and 200 rpm for 4 days at 30 °C. Statistical optimization takes place, where a central composite design was employed for testing the reaction variables. The individual and interactive effects of process variables lead to optimal biosynthesis conditions with 10−4 M (K2TiF6) concentration, for 96 h, 28 °C, pH 9, and Ti+4 salt solution:filtrate ratio (10%, v/v). Kinetic conversion rates in 1-L shake flask and 10-L stirred tank bioreactor were calculated and compared. Current findings revealed that the yield coefficient of biomass dry weight (Yx/s) and the yield coefficient of TiO2 NP dry weight (Y pn/s) in the bioreactor exceed those of the shake flask (0.85 g/L and 0.51 g/L; 0.04 g/L and 0.11 g/L, respectively). TiO2 NPs showed anticancer activities with high biocompatibility (at 1000 µg/mL) against MCF-7 and HepG-2 cell lines, with 97.35% and 97.71% cytotoxicity, respectively. TiO2 NPs had a moderate antioxidant activity of 57.8% recorded by DPPH assay. Moreover, TiO2 NPs had anticoagulant activities and decolorization efficiency for methyl orange dye. The current study paves the way for maximizing TiO2 NP production, which can be used in industrial and medical sectors. Graphical Abstract