Abstract
The remediation of heavy-metal-contaminated sites represents a serious environmental problem worldwide. Currently, cost- and time-intensive chemical treatments are usually performed. Bioremediation by heavy-metal-tolerant microorganisms is considered a more eco-friendly and comparatively cheap alternative. The fungus Penicillium simplicissimum KS1, isolated from the flooding water of a former uranium (U) mine in Germany, shows promising U bioremediation potential mainly through biomineralization. The adaption of P. simplicissimum KS1 to heavy-metal-contaminated sites is indicated by an increased U removal capacity of up to 550 mg U per g dry biomass, compared to the non-heavy-metal-exposed P. simplicissimum reference strain DSM 62867 (200 mg U per g dry biomass). In addition, the effect of temperature and cell viability of P. simplicissimum KS1 on U biomineralization was investigated. While viable cells at 30°C removed U mainly extracellularly via metabolism-dependent biomineralization, a decrease in temperature to 4°C or use of dead-autoclaved cells at 30°C revealed increased occurrence of passive biosorption and bioaccumulation, as confirmed by scanning transmission electron microscopy. The precipitated U species were assigned to uranyl phosphates with a structure similar to that of autunite, via cryo-time-resolved laser fluorescence spectroscopy. The major involvement of phosphates in U precipitation by P. simplicissimum KS1 was additionally supported by the observation of increased phosphatase activity for viable cells at 30°C. Furthermore, viable cells actively secreted small molecules, most likely phosphorylated amino acids, which interacted with U in the supernatant and were not detected in experiments with dead-autoclaved cells. Our study provides new insights into the influence of temperature and cell viability on U phosphate biomineralization by fungi, and furthermore highlight the potential use of P. simplicissimum KS1 particularly for U bioremediation purposes. Graphical
Highlights
As a result of former uranium (U) mining and milling activities, large amounts of wastewater containing high concentrations of U and other heavy metals have been generated, with the potential risk of contaminating the surrounding environment
We focused on changes in the uranium bioremoval by P. simplicissimum KS1 depending on temperature and cell viability to unravel metabolic reliance
The results presented here highlight the potential of the heavy metal-adapted fungal isolate P. simplicissimum KS1 for bioremediation of U- and other heavy-metal-contaminated sites
Summary
As a result of former uranium (U) mining and milling activities, large amounts of wastewater containing high concentrations of U and other heavy metals have been generated, with the potential risk of contaminating the surrounding environment. It is necessary to clean up contaminated sites, and to treat U-contaminated wastewater in order to prevent heavy metal release to the environment. The former U mine in Königstein (Germany) represents such a contaminated site. The flooding water is still characterized by relatively high concentrations of U (~8–9 mg/L) and a low pH of 2.9 owing to the acidic leaching process (Kassahun et al, 2015). The water has to be pumped to the surface and is currently treated by a conventional, chemical wastewater treatment plant
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
