Biological selenite removal and recovery of selenium nanoparticles by haloalkaliphilic bacteria isolated from the Nakdong River

Highlights: • Bacteria isolated from river water could reduce Se (IV) and produce elemental Se. • Strain NDSe-7 could perform Se (IV) reduction at pH 10.0 and salinity of 7%. • An extremotolerant can be isolated from a conventional environment. • Strain NDSe-7 can remove 80 mg/L of Se (IV) within 24 h. Microbial selenite reduction has increasingly attracted attention from the scientific community because it allows the separation of toxic Se from waste sources with the concurrent recovery of Se nanoparticles, a multifunctional material in nanotechnology industries. In this study, four selenite-reducing bacteria, isolated from a river water sample, were found to reduce selenite by > 85% within 3 d of incubation, at ambient temperature. Among them, strain NDSe-7, belonging to genus Lysinibacillus, can reduce selenite and produce Se nanospheres in alkaline conditions, up to pH 10.0, and in salinity of up to 7.0%. This strain can reduce 80 mg/L of selenite to elemental Se within 24 h at pH 6.0–8.0, at a temperature of 30–40 °C, and salinity of 0.1–3.5%. Strain NDSe-7 exhibited potential for use in Se removal and recovery from industrial saline wastewater with high alkalinity. This study indicates that extremophilic microorganisms for environmental remediation can be found in a conventional environment.