Oxidative Stress Induced by Metal Ions in Bioleaching of LiCoO2 by an Acidophilic Microbial Consortium

Abstract

An acidophilic microbial consortium (AMC) was used to investigate the fundamental mechanism behind the adverse effects of pulp density increase in the bioleaching of waste lithium ion batteries (WLIBs). Results showed that there existed the effect of metal-ion stress on the bio-oxidative activity of AMC. The Li + and Co 2+ accumulated in the leachate were the direct cause for the decrease in lithium and cobalt recovery yields under a high pulp density. In a simulated bioleaching system with 4.0% (w •v −1) LiCoO 2 , the intracellular reactive oxygen species (ROS) content in AMC increased from 0.82 to 6.02 within 24 h, which was almost three times higher than that of the control (2.04). After the supplementation of 0.30 g•L −1 of exogenous glutathione (GSH), the bacterial intracellular ROS content decreased by 40% within 24 h and the activities of intracellular ROS scavenging enzymes, including glutathione peroxidase (GSH-Px) and catalase (CAT), were 1.4-and 2.0-folds higher in comparison with the control within 24 h. In the biofilms formed on pyrite in the bioleaching of WLIBs, it was found that metal-ion stress had a great influence on the 3-D structure and the amount of biomass of the biofilms. After the exogenous addition of GSH, the structure and the amount of biomass of the biofilms were restored to some extent. Eventually, through ROS regulation by the exogenous addition of GSH, very high metal recovery yields of 98.1% Li and 96.3% Co were obtained at 5.0% pulp density.

Unlocking Survival Mechanisms for Metal and Oxidative Stress in the Extremely Acidophilic, Halotolerant Acidihalobacter Genus

“…This is consistent with previous studies that suggested proteobacteria have the strongest ROS defense signature across domain bacteria [23,99]. It has also been suggested that during high ROS stress in bacteria, the hydrogen peroxide-inducible genes activator protein regulator (OxyR) is activated and an increased expression and activity of the oxidative stress responses of AhpC and catalase are observed [23,107]. Genes encoding OxyR were identified in all of the Acidihalobacter species.…”

“…It has been shown that the mutual regulation and expression of catalase and ahpC genes results in dual response to oxidative stress [106]. This is consistent with previous studies that suggested proteobacteria have the strongest ROS defense signature across domain bacteria [23,99]. It has also been suggested that during high ROS stress in bacteria, the hydrogen peroxide-inducible genes activator protein regulator (OxyR) is activated and an increased expression and activity of the oxidative stress responses of AhpC and catalase are observed [23,107].…”

“…Previous proteomic studies and comparative genomics have identified mechanisms for chloride tolerance for the members of the Acidihalobacter genus; however, high levels of metal and oxidative stress also represent key factors that can compromise the feasibility of bioleaching of metals from minerals [23,24]. There is a limited understanding of the molecular components involved in defense mechanisms in acidophiles in general and in the recently reclassified species of the Acidihalobacter genus in particular.…”

Understanding Stress Response to High-Arsenic Gold-Bearing Sulfide Concentrate in Extremely Metal-Resistant Acidophile Sulfobacillus thermotolerans

“…The synergistic effect of Li + and Co 2+ , accumulated in the leachate in the simulated bioleaching system with 4.0% of LiCoO 2 slurry, has been shown to cause the oxidative stress in the acidophilic microbial consortium including mainly Sb. thermosulfidooxidans and L. ferriphilum [ 75 ]. Although the oxidative stress results in increased intracellular ROS, the addition of the exogenous glutathione (which acts as an antioxidant) increases the activities of GSH peroxidase and catalase to scavenge the excessive intracellular ROS, and this results in improved bioleaching of LiCO 2 by the community [ 75 ].…”

“…thermosulfidooxidans and L. ferriphilum [ 75 ]. Although the oxidative stress results in increased intracellular ROS, the addition of the exogenous glutathione (which acts as an antioxidant) increases the activities of GSH peroxidase and catalase to scavenge the excessive intracellular ROS, and this results in improved bioleaching of LiCO 2 by the community [ 75 ].…”