Microorganisms (or "Hungry Miners" as we call them) that are currently used in commercial bioleaching operations are so far ubiquitous in nature. Wherever a suitable ore is exposed to the hungry miner and water is present, the naturally occurring microorganisms (MOs) will be found exploiting the resource.The first isolated and best-studied iron and/or sulfur-oxidizing bacterium is Acidithiobacillus ferrooxidans, formerly known as Thiobacillus ferrooxidans. The perceived importance of At. ferrooxidans in bioleaching environments was largely a consequence of the relative ease of its enrichment and isolation, and its rapid growth in acidic iron(II) media, by which it out-competed other members of its microbial community (Watling, H. 2016). The discovery and description of this miner prompted a rapid increase in microbiological studies related to the oxidation of sulﬁde minerals.
The variety of microbes identified as being capable of growth in situations that simulate biomining commercial processes is rapidly growing. This is partly because of an increase in the number of environments being screened for such organisms, partly because of an increase in the variety of minerals being tested, and most of all because of new techniques available to screen for the presence of any organisms. Miners are non-pathogenic and there have been no reports of illness due to these microbes.
HOWEVER - the growth of above-given miners is inhibited or prevented in the presence of organic matter. Therefore the efficiency of bioleaching an ore where metals are trapped in organic complexes is not maximum. The microorganisms also only function in specific temperature ranges, require iron or reduced sulfur as an energy source and in most cases grow optimally at pH < 2.5.
Luckily, one team of Hungry Miners developed in BiotaTec operate best at neutral pH and do excellent work in breaking up organic complexes (porphyrin rings) while simultaneously producing methane gas and freeing metals into the water solution. They also turn toxic sub-products of methanogenesis (NH3, H2, H2S) into non-hazardous products (N2, H2O, S0).
Through massive amount of adaption tests carried out in our lab with very different micro-organisms during the last years we have extended the personnel of Hungry Miners, enabling us to increase the metals extraction rate and speed in different additional step of the biotreatment route.
Peer-reviewed publication about this amazing team is being prepared - stay tuned:-)!