Acidophilic bacteria for metal extraction: biotechnological characteristics and applications

Abstract

Biotechnology has increasing relevance worldwide in the mining sector, either as a response to the recovery of metals (gold, silver, copper, zinc, nickel, among others) as well as an alternative in the bioremediation of contaminated soil and water, frequent problems directly linked to mining activities. Hence, acidophilic microorganisms are of special scientific and industrial interest for the sustainable use of mineral resources. Nowadays, a wide variety of acidophilic chemolithotrophic microorganisms (MOs) are recognized, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus, and Leptospirillum ferrooxidans, among others; those MOs grow in culture medium at pH ≤ 3 and obtain cellular energy from the oxidation of inorganic compounds, such as sulfur and iron. These microorganisms have different abilities to act on the mineral, converting insoluble metal sulfides into soluble metal sulfates of those species that are of interest, or that prevent optimal recovery of a specific mineral. Such microorganisms have been applied in biomining operations and are internationally known for the recovery of valuable metals from low-grade ores and refractory ores. Likewise, these acidophilic MOs can bioremediate soils contaminated with metals, extract metals from sludge generated as a byproduct in wastewater treatment, detoxify hazardous waste and recover metals from electronic waste; so the main interest of biomining processes lies in the economic impact that has benefited the world, since it is known that 5% of the gold and 20% of the copper that has been extracted worldwide are using this type of bacteria in bioleaching processes. The objective of this review is to expand the knowledge of the characteristics and applications of the main acidophilic microorganisms used in the solubilization/extraction of minerals, whether for the recovery of metals, bioremediation, or reduction of metals in different systems.

Graphical abstract

The role of acidophilic bacteria in several industrial sectors. Created with BioRender.com.