RESULTS:

Biomineralization is a ubiquitous process in organisms to produce biominerals and a wide range of metallic nanoscale minerals can be produced as a consequence of the interactions of micro-organisms with metals and minerals. Copper-bearing nanoparticles produced by biomineralization mechanisms have a variety of applications due to their remarkable catalytic efficiency antibacterial properties and low production cost. In this study we demonstrate the biotechnological potential of copper carbonate nanoparticles (CuNPs) synthesized using a carbonate-enriched biomass-free ureolytic fungal spent culture supernatant. The efficiency of the CuNPs in pollutant remediation was investigated using a dye (methyl red) and a toxic metal oxyanion chromate Cr(VI). The biogenic CuNPs exhibited excellent catalytic properties in a Fenton-like reaction to degrade methyl red and efficiently removed Cr(VI) from solution due to both adsorption and reduction of Cr(VI). X-ray photoelectron spectroscopy (XPS) identified the oxidation of reducing Cu species of the CuNPs during the reaction with Cr(VI). This work shows that urease-positive fungi can play an important role not only in the biorecovery of metals through the production of insoluble nanoscale carbonates but also provides novel and simple strategies for the preparation of sustainable nanomineral products with catalytic properties applicable to the bioremediation of organic and metallic pollutants solely and in mixtures.

Microbes play key geoactive roles in the biosphere particularly in the areas of element biotransformations and biogeochemical cycling metal and mineral transformations decomposition bioweathering and soil and sediment formation. All kinds of microbes including prokaryotes and eukaryotes and their symbiotic associations with each other and ‘higher organisms’ can contribute actively to geological phenomena and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation toxicity and mobility as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass soil rocks and minerals e.g. sulfur and phosphorus and metalloids actinides and metal radionuclides. Apart from being important in natural biosphere processes metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution with bacteria and fungi being the most important organisms for reclamation immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle crystalline or colloidal forms and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials rock and mineral-based building materials (e.g. concrete) acid mine drainage and associated metal pollution biocorrosion of metals alloys and related substances and adverse effects on radionuclide speciation mobility and containment all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.