The demand for rare earth elements (REEs) has grown like an avalanche in recent decades. They are now used in virtually every area of the global economy, from lasers and mobile phones, car catalysts and artificial diamonds up  to fertilisers, spacecraft and medical equipment.

The world production of REE has been controlled by China (85 per cent), but Russia's share is only about two per cent. The discovery of scientists at the Kola Science Centre and the Komarov Botanical Institute has the potential to increase the amount of rare earth elements mined.

The main economic sources of rare-earth elements are the minerals bastnasite (REE-FCO3), monazite (light REE-PO4) and xenotime (heavy REE-PO4). Loparite (Na,Ca,Ce,Sr)2(Ti,Ta,Nb)2O6 may also be considered as a REE source. According to recent studies carried out by scientists of the Kola Science Centre, underground in the Murmansk region, there are almost $700 billion worth of rare-earth element reserves.

There is also the only functioning deposit of loparite, which is extracted and processed at the Lovozersky Mining and Processing Combine. The loparite concentrate produced at the plant is a complex raw material for further production of niobium, tantalum, rare-earth elements of the cerium group and titanium. Traditional methods of extracting REE ores involve heating and the use of hazardous acids. This is very expensive, energy consuming and has a negative impact on the environment.

Recently, there has been a growing interest in nature-like, i.e. mimicking natural processes, technologies in various fields, such as bioleachingthe extraction of substances from natural and anthropogenic raw materials using bacteria and microscopic fungi.

Scientists from the Institute of Industrial Ecology Problems of the North, Kola Science Centre, and the Komarov Botanical Institute have studied the ability of certain species of microfungi to accumulate rare-earth elements from loparite production waste.

An article about this has been  published in the international Geomicrobiology Journal.

Samples from two tailings sites where loparite concentrate wastes are accumulated have been examined by inductively coupled plasma mass spectroscopy to determine their composition.

The microorganisms found in the samples have been cultured in Petri dishes filled with nutrient medium specially designed to promote fungal growth and inhibit bacterial growth. In this way, the most characteristic species have been  identified and isolated. The dominant species Geomyces vinaceus and Penicillium simplicissimum, the non-dominant Aspergillus niveoglaucus and Pseudogymnoascuc pannorum, and the control strain Cadophora malorum have been  tested for tolerance and resistance to neodymium and cerium.

During the study, the scientists noted, that the microscopic fungi adapted to the stress induced by elevated levels of rare earth elements. Low concentrations in all strains caused a slight increase in growth rate and colony size with no change in colony structure. This may indicate the stimulating nature of low doses of REE for the growth of microfungi. At high levels of REE in the medium, there was a change in the morphology and suppression of microfungi growth. For example, at the highest doses of cerium chloride, Pseudogymnoascuc pannorum colonies lost their characteristic structure and resembled slimy colonies of yeast forms of fungi.

As a result, Penicillium simplicissimum was the most tolerant to both elements and continued growing at the highest (500 mg/l) REE concentrations. Geomyces vinaceus was resistant only to neodymium and more sensitive to cerium. Both of these species are very unpretentious, cold-resistant and capable of colonizing areas disturbed by mining. The study showed that Penicillium simplicissimum can extract rare-earth elements from loparite ore tailings.

The researchers believe that their results will allow them to evaluate the possibility of using the tested fungi for bioleaching of rare earth elements. Further,  in-depth research, it  is needed to better understand the bioleaching potential of microscopic fungi in large-scale industrial processes and the development of nature-like technologies.