Application of Freeze-Dried Powders of Genetically Engineered Microbial Strains as Adsorbents for Rare Earth Metal Ions

Abstract

The adsorption behaviors of the rare earth metal ions onto freeze-dried powders of genetically engineered microbial strains were compared. Cell powders obtained from four kinds of strains, Bacillus subtilis 168 wild type (WT), lipoteichoic acid-defective (ΔLTA), wall teichoic acid-defective (ΔWTA), and cell wall hydrolases-defective (EFKYOJLp) strains, were used as an adsorbent of the rare earth metal ions at pH 3. The adsorption ability of the rare earth metal ions was in the order of EFKYOJLp > WT > ΔLTA > ΔWTA. The order was the same as the order of the phosphorus quantity of the strains. This result indicates that the main adsorption sites for the ions are the phosphate groups and the teichoic acids, LTA and WTA, that contribute to the adsorption of the rare earth metal ions onto the cell walls. The contribution of WTA was clearly greater than that of LTA. Each microbial powder was added to a solution containing 16 kinds of rare earth metal ions, and the removals (%) of each rare earth metal ion were obtained. The scandium ion showed the highest removal (%), while that of the lanthanum ion was the lowest for all the microbial powders. Differences in the distribution coefficients between the kinds of lanthanide ions by the EFKYOJLp and ΔWTA powders were greater than those of the other strains. Therefore, the EFKYOJLp and ΔWTA powders could be applicable for the selective extraction of the lanthanide ions. The ΔLTA powder coagulated by mixing with a rare earth metal ion, although no sedimentation of the WT or ΔWTA powder with a rare earth metal ion was observed under the same conditions. The EFKYOJLp powder was also coagulated, but its flocculating activity was lower than that of ΔLTA. The ΔLTA and EFKYOJLp powders have a long shape compared to those of the WT or ΔWTA strain. The shapes of the cells will play an important role in the sedimentation of the microbial powders with rare earth metal ions. As the results, three kinds of the genetically engineered microbial powders revealed unique adsorption behaviors of the rare earth metal ions.

Adsorption of Rare Earth Elements onto DNA-Functionalized Mesoporous Carbon

“…This essentially suggests that Nd­(III) adsorption is most effective in the lower dose. The adsorbed amount and distribution coefficient of Nd in MC-T100 are higher than those of other DNA-based materials, such as salmon milt powder or DNA-filter hybrid and other sorbents, including freeze-dried powder of genetically engineered microbial strains, EDTA- and DTPA-functionalized chitosan, and ion-imprinted mesoporous silica …”

“…Our previous research demonstrated a higher uptake of Nd and Dy compared to Fe­(III) in phosphorous-functionalized microporous carbon . The cell walls of different types of natural or genetically modified bacteria were employed for the capture of various REEs, and it was hypothesized that the phosphate functionality on the cell wall of bacteria strains is responsible for the affinity-based capture of these rare earth elements. , Recently, commercially available DNA-based materials have been employed to selectively capture REEs through their phosphorous and oxygen functionalities. Freeze-dried and powdered salmon milt as a source of DNA was employed to adsorb 15 REEs in a column process .…”

Microbe-Encapsulated Silica Gel Biosorbents for Selective Extraction of Scandium from Coal Byproducts

“…It is worth noting that the selectivity for Sc over Y and Nd was also observed for cell-free silica (Figure S3), albeit with much lower total adsorption compared to that of MESG (Figure S4). The selectivity of the MESG biosorbent for Sc is likely attributed to the ability of cell surface hard ligands (i.e., phosphate groups) and silanol groups on silica to form strong complexes with Sc­(III) ions, which has a smaller ionic radius and stronger Lewis acid characteristics compared to that of the lanthanides. , …”

“…Solid–liquid extraction (SLE) has emerged as an attractive alternative for Sc extraction due to the elimination of toxic, inflammable, and expensive organic solvents (diluent + extractant) and the facile reuse of adsorbent materials . A number of adsorbent materials have been developed for Sc recovery, including polyelectrolytes, carbon-based materials, polymer resins, and silica. − These adsorbents exhibit high Sc adsorption capacity owing to their high surface area and abundant negatively charged functional groups, , but their utility to extract Sc in the presence of competing lanthanides remains largely unknown, a barrier for their application to low-grade Sc feedstocks. ,,,,, Microbe-mediated surface adsorption (biosorption) via metal complex formation with the surface functional group offers a potentially cost-effective and environmentally sustainable approach for SLE of REE from dilute feedstock sources. − Previous work has shown that Sc was preferentially adsorbed to Bacillus subtilis and Escherichia coli when Sc was present at the same concentrations as the lanthanides. , Several yeast species were found to preferentially adsorb Sc over Y, Fe, and Al in both synthetic solutions and red mud leachates . While these initial studies are promising, it remains an open question, however, whether biosorption can be effectively applied for selective and scalable Sc recovery from relevant industrial feedstocks.…”

“…33−36 Previous work has shown that Sc was preferentially adsorbed to Bacillus subtilis and Escherichia coli when Sc was present at the same concentrations as the lanthanides. 37,38 Several yeast species were found to preferentially adsorb Sc over Y, Fe, and Al in both synthetic solutions and red mud leachates. 39 While these initial studies are promising, it remains an open question, however, whether biosorption can be effectively applied for selective and scalable Sc recovery from relevant industrial feedstocks.…”