Abstract
Microfungi were able to alternate solid substrate in various environments and play a noticeable role in the formation of insoluble calcium oxalate crystals in subaerial biofilms on rock surfaces. The present work describes how iron oxalate dihydrate humboldtine is acquired under the influence of the acid-producing microscopic fungus Aspergillus niger on the surface of two iron- bearing mineral substrates in vitro. Pyrrhotite and siderite rocks, as well as the products of their alteration, were investigated using a complex of analytical methods, including powder X-ray diffraction, optical microscopy, scanning electron microscopy and EDX spectroscopy. The effect of the underlying rocks with different composition and solubility and different oxidation states of iron on Fe-oxalate crystallization and on the morphology of humboldtine crystals was shown. The mechanisms of humboldtine formation were discussed. The results obtained in vitro seem promising for using fungi in bioleaching iron and other metals from processed ores and for the development of environmentally friendly biotechnologies.
Highlights
Microscopic fungi play a significant role in the biological colonization of rocks, causing their biochemical alteration
A. niger on theiron surface of two iron-bearing mineral unde experimental study, obtained oxalate dihydrate humboldtine substrates differing by iron oxidation state and by solubility. minera the action of the acid-producing fungus A. niger on the surface of two iron-bearing
Both underlying rocks dissolved significantly under the action of substrates differing by iron oxidation state and by solubility
Summary
Microscopic fungi play a significant role in the biological colonization of rocks, causing their biochemical alteration. The formation of insoluble biogenic oxalates on the surface of rocks is often observed under the action of acid-producing fungi [1,2,3]. It is important to understand the mechanisms of the interaction between lithobiotic microorganisms and rocks, which lead to biomineralization processes [4,5]. Fungi involved in these processes can be utilized for biotechnologies [6]. It is a widespread chemical element and exists in the Earth crust in bivalent and trivalent states in the form of various compounds (oxides, carbonates, salts etc.)
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