Nickel-Tolerant Aspergillus flavus as a Sustainable Agent for Nickel Bioremediation

The large-scale use of nickel (Ni [II]) in many industrial processes results in the production of Ni-containing wastes, posing a hazardous impact on public health and the environment. The current study highlights Aspergillus flavus's potential for environmental bioremediation and the impact of Ni stress on the growth kinetics, removal efficiency and bioaccumulation. The results showed that the biomass of A. flavus decreased at all tested Ni (II) concentrations as compared to the control. Additionally, the minimal inhibitory concentration (MIC) of A. flavus was 4500 mg L^- 1 on solid medium. The Ni (II) removal rate of A. flavus increased with increasing Ni (II) levels and peaked at 63.76% at 750 mg L^- 1, while the maximum bioaccumulation capacity (Q) reached 83.07 mg g^- 1 at 1750 mg L^- 1. Moreover, Ni (II) stress caused an increase in malondialdehyde (MDA) (137.74% at 1750 mg L^- 1). Antioxidant enzyme activities and secondary metabolites significantly increased to counteract oxidative stress before declining at extreme concentrations. Also, Fourier-transform infrared spectroscopy (FTIR) demonstrated that amide, phosphate, and sulfur groups participate in Ni (II) biosorption as accumulation sites. Furthermore, energy-dispersive X-ray (EDX) spectroscopy confirmed the presence of Ni (II) on the mycelial surface, with a measured weight% of 9.44%. Notably, our study reveals a synergistic network of defense mechanisms that support A. flavus's resilience. These results emphasize the work's novelty and substantiate the isolate's use as a feasible option for long-term bioremediation.