General Description

Scandium, a rare earth element, is crucial for high-tech industries due to its use in aerospace, military, pharmaceuticals, and medical technologies. However, challenges in mining and purification lead to high costs and environmental impact. Its impact on microorganisms varies, showing lower toxicity to certain bacteria and potential antimicrobial effects. Scandium bioaccumulation by diverse microorganisms offers promise for environmental applications and novel methods for rare earth element separation. Addressing these complexities is essential for sustainable technological advancement and environmental remediation. Further research is needed to fully understand the impact of scandium on microorganisms and develop effective, eco-friendly mining technologies.

Figure 1. Scandium

Importance

Scandium, a rare earth element, holds significant importance due to its widespread applications in high-tech industries. Its use in producing high-quality multicomponent alloys is crucial for creating lightweight, stable, and high-stiffness structures for aerospace and military purposes. Additionally, Scandium shows promise in developing new technologies in pharmaceuticals, diagnostics, and medical industries. Despite its abundance in the Earth's crust, the mining and purification of Scandium pose significant challenges, including high dispersity, technological difficulties, energy inefficiency, expensive reagents, and environmental pollution. The global demand for Scandium continues to rise, yet its scarcity and monopolization in certain regions have led to increased prices, posing a threat to global technological and sustainable development. As a result, there is an urgent need for the development of effective, profitable, and eco-friendly Scandium mining technologies. Addressing these challenges in Scandium production is crucial for meeting the growing market demand, reducing reliance on monopolized sources, and supporting sustainable technological advancement across various industries. ¹

Effects on Microorganisms

Scandium is commonly found in environments where microorganisms thrive, such as oceans, lakes, soils, and industrial areas. Despite this ubiquitous presence, the impact of Scandium on microorganisms, including bacteria, fungi, and algae, remains poorly understood. Research has shown varying levels of toxicity of Sc towards different microorganisms, with minimum inhibitory concentrations ranging from 1.0 mM to 15.0 mM. Studies have indicated that Scandium ions exhibit lower toxicity to certain bacteria like E. coli and Staphylococcus aureus compared to ions of silver or copper. However, the toxicity of Scandium to other organisms like Aspergillus niger and Penicillium citrinum falls between that of silver and copper. Additionally, Scandium has been observed to enhance the antibacterial effects of zinc against E. coli and S. aureus by increasing the production of reactive oxygen species. While Scandium itself may not possess strong antimicrobial properties, mutations in certain microorganisms, such as Bacillus subtilis, have led to the development of Sc-resistant phenotypes. These mutations often involve genes related to cell wall synthesis, such as the uppS gene encoding undecaprenyl pyrophosphate synthase. Mutations in this gene have been linked to increased susceptibility to Sc, while overexpression of the wild-type gene enhances resistance not only to Sc but also to other rare earth elements and antibiotics like bacitracin. In summary, the effects of Scandium on microorganisms are complex, involving varying levels of toxicity and interactions that can influence microbial metabolism and resistance mechanisms. Further research is needed to fully elucidate the impact of Scandium on different types of microorganisms and their ecosystems. ²

Bioaccumulation

The bioaccumulation of scandium by living microorganisms is facilitated by the presence of multiple binding sites on microbial cell structures, allowing for interaction with scandium ions or compounds. This process involves various microorganisms, including bacteria, fungi, yeasts, and algae, each demonstrating different capacities for Sc accumulation. Notably, Gram-positive bacteria such as Bacillus species exhibit a high capacity for scandium accumulation, while unicellular algae like Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata also accumulate Sc in specific complexes. The bioaccumulating capacity of different microbial genera follows a distinct order, with Bacillus, Streptomyces, Pseudomonas, Mucor, Aspergillus, and Candida showing varying degrees of scandium accumulation ability. Furthermore, studies have highlighted the potential for leveraging the adsorption capacity of microbial biomass in the development of novel methods for rare earth element (REE) separation, with scandium displaying a higher affinity for organisms compared to other REEs. Additionally, the role of siderophores, specific membrane proteins, and metabolic changes in the process of scandium bioaccumulation has been investigated, providing insights into the complex mechanisms underlying this phenomenon. Overall, understanding scandium bioaccumulation by microorganisms holds significant promise for applications in environmental remediation, biogeochemical cycling, and the development of new methods for Sc separation and concentration. ²

Reference

1. Botelho J, et al. Recovery of scandium from various sources: a critical review of the state of the art and future prospects. Miner Eng. 2021; 172: 107148.

2. Syrvatka V, Rabets A, Gromyko O, Luzhetskyy A, Fedorenko V. Scandium-microorganism interactions in new biotechnologies. Trends Biotechnol. 2022; 40(9): 1088-1101.