Thermophilic microorganisms in biomining

Abstract

Biomining is an applied biotechnology for mineral processing and metal extraction from ores and concentrates. This alternative technology for recovering metals involves the hydrometallurgical processes known as bioleaching and biooxidation where the metal is directly solubilized or released from the matrix for further solubilization, respectively. Several commercial applications of biomining can be found around the world to recover mainly copper and gold but also other metals; most of them are operating at temperatures below 40-50 °C using mesophilic and moderate thermophilic microorganisms. Although biomining offers an economically viable and cleaner option, its share of the world´s production of metals has not grown as much as it was expected, mainly considering that due to environmental restrictions in many countries smelting and roasting technologies are being eliminated. The slow rate of biomining processes is for sure the main reason of their poor implementation. In this scenario the use of thermophiles could be advantageous because higher operational temperature would increase the rate of the process and in addition it would eliminate the energy input for cooling the system (bioleaching reactions are exothermic causing a serious temperature increase in bioreactors and inside heaps that adversely affects most of the mesophilic microorganisms) and it would decrease the passivation of mineral surfaces. In the last few years many thermophilic bacteria and archaea have been isolated, characterized, and even used for extracting metals. This paper reviews the current status of biomining using thermophiles, describes the main characteristics of thermophilic biominers and discusses the future for this biotechnology.

In a quest for engineering acidophiles for biomining applications: challenges and opportunities

“…The slow oxidation rate of mineral substrates by biomining microbes is one of the main reasons of their limited industrial implementation, especially for chalcopyrite processing [ 126 ]. The use of thermophiles can overcome this bottleneck as higher operational temperature can increase the rate of the oxidation, reduce the time for metal solubilisation, eliminate the need for cooling the system, and decrease the passivation of mineral surfaces [ 127 ]. Biomining processes above 60 °C usually involve iron and sulfur oxidising archaea, which belong to the genera Sulfolobus , Acidianus , Metallosphaera , and Sulfurisphaera [ 127 ].…”

Metal-Tolerant Thermophiles: From the Analysis of Resistance Mechanisms to their Biotechnological Exploitation

“…Biomining refers to the exploitation of microorganisms to extract and recover metals from ores and waste concentrates (the term is often used synonymously with bioleaching when the metals are solubilized during the process); on the other hand, bioremediation focuses on the transformation of a toxic substance into a harmless or less toxic one from contaminated sites [82,83]. In this contest, among the heavy metals resistance systems developed by microorganisms, and in particular by thermophiles, biosorption and bioaccumulation are emerging as promising lowcost methodologies for bioremediation [84,85]. Biosorption and bioaccumulation are two processes that consist into the ability of microorganisms to accumulate heavy metals from wastewater through metabolic pathways or physicalchemical uptake; but while biosorption is a passive process depending on the composition of the cellular surface and following a kinetic equilibrium, bioaccumulation is an energy driven process and requires an active metabolism [59].…”

Sulfolobus – A Potential Key Organism in Future Biotechnology

“…Thermophiles gain increasing attention in biotechnological applications due to their potential to expand the thermal range of industrial biotechnology and their unique metabolic capabilities ( Littlechild, 2015 ; Zeldes et al, 2015 ; Beeler and Singh, 2016 ; Donati et al, 2016 ; Basen and Müller, 2017 ; Straub et al, 2017 ). In this review, we focus on the well-characterized members of the phylum Crenarchaeota, the extreme thermoacidophilic Archaea belonging to the genus Sulfolobus .…”