As concerns are increasing about drinking water contamination with heavy metals, we investigated the possible use of a pellicle (floating biofilm)-like biofilm-producing microorganism as a biosorbent for the treatment of Pb(II) in aqueous solutions. The bacterial pellicle-producing Methylobacterium hispanicum EM2 strain (EM2) was newly isolated from mine tailing soil, and we investigated its use as a biosorbent for treating a Pb(II)-contaminated aqueous solution. The EM2 strain was strongly resistant to Pb(II) up to a concentration of 800 mg/L, and achieved remarkable adsorption performance (adsorption rate and maximum adsorption capacity of 96% ± 3.2% and 79.84 mg/g, respectively) under optimal conditions (pH, biomass content, contact time, and initial Pb(II) concentration of 7.1 g/L, 60 min, and 10 mg/L, respectively). The adsorption of Pb(II) was characterized by scanning electron microscopy-energy dispersive x-ray spectroscopy and Fourier-transform infrared analysis. The equilibrium data matched the Freundlich isotherm model well, indicating the occurrence of multilayer adsorption of Pb(II) onto the heterogeneous surface of the EM2 strain, which was also consistent with the pseudo-second-order kinetic model (R² = 0.98). The high Pb(II) removal efficiency was also confirmed by conducting an adsorption experiment using Pb(II)-contaminated industrial wastewater.

As concerns about public health and environmental problems regarding contamination by toxic substances increase worldwide, the development of a highly effective and specific treatment method is imperative. Although physicochemical arsenic treatment methods have been developed, microbial in vivo remediation processes using live cell fabricated nanoparticles have not yet been reported. Herein, we report the development of magnetic iron nanoparticles immobilized an extremophilic microorganism, Deinococcus radiodurans R1, capable of removing toxic arsenic species. First, in vivo synthesis of magnetic iron nanoparticles was successfully achieved with the D. radiodurans R1 strain and characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), dynamic light scattering (DLS), zeta-potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Second, the maximum removal capacity of the magnetic iron nanoparticle-immobilized D. radiodurans R1 strain (DR-FeNPs) for arsenic [As(V)] was evaluated under the optimized conditions. Finally, the removal capacity of DR-FeNPs in the presence of various competitive anions was also investigated to simulate the practical application. More than 98% of As(V) was efficiently removed by DR-FeNPs within 1 h, and the removal efficiency was stably maintained for up to 32 h (98.97%). Furthermore, the possibility of recovery of DR-FeNPs after use was also suggested using magnets as a proof-of-concept.