Large Amounts Of Copper Research Articles

Hetero-Diels-Alder and CuAAC Click Reactions for Fluorine-18 Labeling of Peptides: Automation and Comparative Study of the Two Methods.

Radiolabeled peptides are valuable tools for diagnosis or therapies; they are often radiofluorinated using an indirect approach based on an F-18 prosthetic group. Herein, we are reporting our results on the F-18 radiolabeling of three peptides using two different methods based on click reactions. The first one used the well-known CuAAC reaction, and the second one is based on our recently reported hetero-Diels-Alder (HDA) using a dithioesters (thia-Diels-Alder) reaction. Both methods have been automated, and the 18F-peptides were obtained in similar yields and synthesis time (37-39% decay corrected yields by both methods in 120-140 min). However, to obtain similar yields, the CuAAC needs a large amount of copper along with many additives, while the HDA is a catalyst and metal-free reaction necessitating only an appropriate ratio of water/ethanol. The HDA can therefore be considered as a minimalist method offering easy access to fluorine-18 labeled peptides and making it a valuable additional tool for the indirect and site-specific labeling of peptides or biomolecules.

Contemporary and Future Secondary Copper Reserves of Vietnam

As ASEAN countries, including Vietnam, approach the living standards of developed countries, their copper demand is set to rise. This study investigates Vietnam’s copper stock and flow from 1995 to 2050, employing dynamic material flow analysis and five socioeconomic pathway scenarios (SSPs). Based on this, the secondary copper reserves of Vietnam were assessed. The results showed that the domestic copper demand is expected to grow to 526–1062 kt, resulting in a rapid increase in scrap generation. In 2022, Vietnam’s secondary copper reserves stood at 2.2 Mt and are projected to reach 6.8–8.6 Mt by 2050 under the SSP2 scenario. This corresponds to 3.6–4.6 times the 1.8 Mt primary copper reserve of Vietnam. However, these primary and secondary reserves cannot meet the cumulated demand by 2050. On the other hand, a large amount of copper, 8.9 Mt to 10 Mt, will become difficult-to-recover resources, such as waste in landfill sites, dissipated materials, or mixed metal loss. To promote the sustainable use of copper in Vietnam, we recommend increased geological expedition and mining investment, and improved waste management systems related to secondary resources.

Nodule-specific Cu+ -chaperone NCC1 is required for symbiotic nitrogen fixation in Medicago truncatula root nodules.

Cu+ -chaperones are a diverse group of proteins that allocate Cu+ ions to specific copper proteins, creating different copper pools targeted to specific physiological processes. Symbiotic nitrogen fixation carried out in legume root nodules indirectly requires relatively large amounts of copper, for example for energy delivery via respiration, for which targeted copper deliver systems would be required. MtNCC1 is a nodule-specific Cu+ -chaperone encoded in the Medicago truncatula genome, with a N-terminus Atx1-like domain that can bind Cu+ with picomolar affinities. MtNCC1 is able to interact with nodule-specific Cu+ -importer MtCOPT1. MtNCC1 is expressed primarily from the late infection zone to the early fixation zone and is located in the cytosol, associated with plasma and symbiosome membranes, and within nuclei. Consistent with its key role in nitrogen fixation, ncc1 mutants have a severe reduction in nitrogenase activity and a 50% reduction in copper-dependent cytochrome c oxidase activity. A subset of the copper proteome is also affected in the ncc1 mutant nodules. Many of these proteins can be pulled down when using a Cu+ -loaded N-terminal MtNCC1 moiety as a bait, indicating a role in nodule copper homeostasis and in copper-dependent physiological processes. Overall, these data suggest a pleiotropic role of MtNCC1 in copper delivery for symbiotic nitrogen fixation.

HORMETIC EFFECT ON THE TOXIC ACTION OF COPPER IONS DEPENDS ON THE TISSUE DISTRIBUTION OF COPPER IONS

The role of inter-tissue localization of copper ions in the processes of hormesis to copper sulfate was investigated. The ability of the liver, spleen, heart, brain, and kidneys to bind copper ions was determined in cases of lethal outcomes after a single administration of copper sulfate to animals (Wistar rats) and in cases of hormesis to this compound. Copper ions in the tissues were determined by atomic absorption spectrometry. It was shown that the hormetic effect depends on the inter-tissue distribution of copper ions, and a relatively large amount of copper can be deposited by serum proteins.

The Role of Copper Homeostasis in Brain Disease.

In the human body, copper is an important trace element and is a cofactor for several important enzymes involved in energy production, iron metabolism, neuropeptide activation, connective tissue synthesis, and neurotransmitter synthesis. Copper is also necessary for cellular processes, such as the regulation of intracellular signal transduction, catecholamine balance, myelination of neurons, and efficient synaptic transmission in the central nervous system. Copper is naturally present in some foods and is available as a dietary supplement. Only small amounts of copper are typically stored in the body and a large amount of copper is excreted through bile and urine. Given the critical role of copper in a breadth of cellular processes, local concentrations of copper and the cellular distribution of copper transporter proteins in the brain are important to maintain the steady state of the internal environment. The dysfunction of copper metabolism or regulatory pathways results in an imbalance in copper homeostasis in the brain, which can lead to a myriad of acute and chronic pathological effects on neurological function. It suggests a unique mechanism linking copper homeostasis and neuronal activation within the central nervous system. This article explores the relationship between impaired copper homeostasis and neuropathophysiological progress in brain diseases.

Exposure to copper activates mitophagy and endoplasmic reticulum stress-mediated apoptosis in chicken (Gallus gallus) cerebrum.

A large amount of copper (Cu) used in production activities can lead to the enrichment of Cu in the environment, which can cause toxicity to animals. However, the toxicity mechanism of Cu on the cerebrum is still uncertain. Hence, a total of 240 chickens were separated into four groups in this study to reveal the potential connection between mitophagy and endoplasmic reticulum (ER) stress-mediated apoptosis in the chicken cerebrum in the case of excess Cu exposure. The cu exposure situation was simulated by diets containing various levels of copper (11 mg/kg, control group; 110 mg/kg, group I; 220 mg/kg, group II and 330 mg/kg, group III) for 49 days. The results of histology showed that vacuolar degeneration was observed in the treated groups, and the mitochondria swell and autophagosomes formation were found under excess Cu treatment. Additionally, the expression of mitophagy (PINK1, Parkin, LC3I, LC3II and p62) and ER stress (GRP78, PERK, ATF6, IRE1α, XBP1, CHOP, and JNK) indexes were significantly upregulated under excess Cu exposure. Furthermore, the mRNA and protein expression of Bcl-2 were decreased, while Bak1, Bax, Caspase12, and Caspase3 were increased compared to the control group. In summary, this study demonstrated that an overdose of Cu could induce mitophagy and ER stress-mediated apoptosis in the chicken cerebrum. These findings revealed an important potential connection between Cu toxicity and cerebrum damage, which provided a new insight into Cu neurotoxicity.

Corrosion and degradation behavior of aluminum and copper refrigerant piping

AbstractMany types of refrigerant piping use copper alloys because of such alloys' high workability, thermal conductivity, and weatherability. However, copper is the 25th most abundant element in Earth's crust (as indicated by its Clark number: a relatively low value, ca. 0.01). Therefore, there is concern about depletion, if emerging countries and new devices such as electric vehicles use large quantities of copper. Recently, we have focused on aluminum as a lightweight metal, which is 4th place in terms of Clark number (ca. 7.6). Refrigerant piping also uses aluminum in air conditioning equipment; thus, practical applications are available. Aluminum alloys used as material for piping also contain other elements such as manganese, silicon, magnesium, copper, and iron. Regarding practical use for pipework, long‐term evaluation (more than 20 years) by corrosion is necessary. Therefore, in this study, we investigated the corrosion‐resistant characteristics of various aluminum alloys by accelerated degradation tests with changing storage conditions, such as temperature and atmosphere. In general, the corrosion of the piping materials depends on the contact atmosphere and differs between inside (refrigerant) and outside (e.g., air) piping. Specifically, there are concerns about the acid of refrigerant oils (inside piping) and corrosion by the salts in seawater (outside piping). The results from immersion tests in refrigerant and cyclic corrosion tests (intermittent cycles between salt mist and drying) proved that aluminum alloys can be used for refrigerant piping in the same way as copper materials.

MO438: Excessive Mitochondrial Copper Load Driven by Upregulated Copper Transporter 1 Contributes to Mitochondrial Dysfunction and Renal Fibrosis

Abstract BACKGROUND AND AIMS Copper is an essential trace element for eukaryotes and a vital cofactor for various enzymes for a multiplicity of functions. Our previous study indicated that intracellular copper overload plays an important role in renal fibrosis. However, the underlying mechanism invoked by copper overload in renal fibrosis remains largely unknown. In this study, we found copper ions in cells were mainly accumulated in mitochondria, which damage the structure and function of mitochondria. Furthermore, copper transporter 1 (CTR1), the major transporter for the copper influx, was significantly increased in fibrotic kidneys. The activity of cytochrome C oxidase (COX), a copper coenzyme mediating the final step in the electron transport chain, was decreased. Therefore, we proposed that CTR1 might be involved in mitochondrial copper overload and renal fibrosis. METHOD The expression of CTR1 was examined in ischemia-reperfusion injury (IRI 28d) mice model. The regulatory mechanisms of CTR1 in vitro were investigated by treating renal tubule epithelium cell line (NRK-52E) with TGF-β1 or copper ions with or without copper chelator tetrathiomolybdate (TM) and in vivo, we use CTR1 transgenic mice subjected to IRI operation. ICP-MS, mitoSOX Red, electron microscopy, realtime-PCR and western blot analysis were applied in the current study. RESULTS We found that stimulated by TGF-β1, COX activity was declined. Mitochondria and cytosol, especially mitochondria, accumulated a large amount of copper in fibrotic kidney tissues. Furthermore, we found Copper transporter 1 (CTR1) expression was increased in fibrotic kidneys from chronic kidney disease patients, experimental fibrosis model mice and in vitro. More importantly, compared with WT mice, CTR1+/- mice subjected to an ischemia-reperfusion injury (IRI) had reduced mitochondrial copper level and ameliorated mitochondrial function and renal fibrosis, as evidenced by improving mitochondrial structure, inhibiting mtROS production and reducing expression of α-smooth muscle actin (α-SMA), collagen I and fibronectin. In addition, after treatment with the copper chelator tetrathiomolybdate (TM), mitochondrial function and kidney fibrosis were improved. CONCLUSION Collectively, our study showed that copper overload in mitochondria could damage the mitochondrial function and lead to renal fibrosis and CTR1 is involved in the mitochondrial copper overload. Copper overload inhibits the activity of COX and impairs mitochondria, subsequently leading to renal fibrosis.

High performing additively manufactured bone scaffolds based on copper substituted diopside

The inclusion of small amounts of copper is often reported to enhance the mechanical and biointegrative performance of bioceramics towards tissue engineering applications. In this work, 3D scaffolds were additively manufactured by robocasting of precipitation derived copper doped diopside. Compositions were chosen in which magnesium sites in diopside were substituted by copper up to 3 at.%. Microstructure, mechanical performance, bioactivity, biodegradability, drug release, biocompatibility, in vitro angiogenesis and antibacterial activity were studied. Results indicate that copper is incorporated in the diopside structure and improves materials’ fracture toughness. Scaffolds with > 80% porosity exhibited compressive strengths exceeding that of cancellous bone. All compositions showed bioactivity and drug release functionalities. However, only samples with 0–1 at.% copper substitution showed favorable proliferation of osteogenic sarcoma cells, human umbilical vein endothelial cells and fibroblasts, while larger amounts of copper had cytotoxic behavior. In vitro angiogenesis was significantly enhanced by low levels of copper. Copper-containing materials showed anti-Escherichia coli activity, increasing with copper content. We show that across multiple indicators, copper substituted diopside of the composition CaMg0.99Cu0.01Si2O6, exhibits high performance as a synthetic bone substitute, comparing favorably with known bioceramics. These findings present a pathway for the enhancement of bioactivity and mechanical performance in printable bioceramics.

The fracture mechanism of Cu3Sn-microporous copper composite joint by thermal compression bonding process

The bonding performances of the composite joint that made of microporous copper and Sn were investigated in this paper. It could rapidly generate .The Cu3Sn- microporous copper composite joint with a thickness of 100 μm was successfully obtained after bonding at 360 °C for 5 min under a low pressure of 0.6 MPa.The shear strength of the composite joint reached 166.05 MPa, which was 2.5 times higher than that of full Cu3Sn joint. The fracture mechanism of composite joint was analyzed by fracture morphology.A large amount of copper could be observed in the fractured surface of composite joint.The self-locking structure was generated between the Cu3Sn and microporous copper in the composite joint.The microporous copper provided more nucleation particles during the formation of Cu3Sn and finally resulted in the refinement of the Cu3Sn grains. In addition,the occurrence of fracture was delayed due to the plastic deformation of microporous copper.

Effect of copper addition on cobalt-molybdenum electrodeposited coatings for the hydrogen evolution reaction in alkaline medium

Co–Mo materials have been reported as electrocatalysts that present good performance in alkaline electrolytes. In this paper, the addition of copper into Co–Mo catalysts was evaluated for the hydrogen evolution reaction (HER). It was observed that the electrochemical activity of the Co–Mo for the HER benefited from the addition of copper. The overpotentials required to reach a current density of −10 mA cm−2 were of −156 mV and −119 mV for Co67Mo33 and Co56Mo21Cu23, respectively. Besides the increased surface area resulting from the addition of copper, it was observed that the improved intrinsic activity for Co61Mo32Cu7, compared to Co67Mo33, is related to a thermodynamic favoring of the hydrogen adsorption and desorption stages. Large quantities of copper do not favor the HER; therefore, the increased catalytic activity depends on a balance between the intrinsic catalytic activity and the increase of the electroactive area.

Removal of Cu from Printed Circuit Board (PCBs) Leachates using Activated Carbon Derived from Foxtail Palm Fruit

Printed circuit boards (PCBs) are the e-waste generated from the end-of-life electronic equipment such as laptops and mobile phone. PCBs contain relatively abundant of valuable metals such as gold and platinum. However, e-waste is considered as an environmental contaminant as it consists plenty of hazardous materials such as cadmium and copper which can pose health threat to human and also environment. It has been reported that PCBs contain a large amount of copper (Cu) in the circuit boards as it is used as a base metal. Moreover, exposure to Cu will lead to adverse impact of human health. Therefore, the objective of the study is to determine the Cu concentration using FAAS and also to remove the Cu from PCBs leachate using activated carbon derived from foxtail palm fruits. In order to remove the Cu, hydrometallurgical process on PCBs will be conducted to leach the metal into solution. Once the metal has been leached to the solution, the metal removal process using activated carbon through adsorption process was conducted. In this study, foxtail palm fruit was tested as an effective low-cost adsorbent for Cu removal. The effect of adsorbent dosage (1 g and 5 g) with fix contact time (40 min) of the prepared activated carbon in selected metal removal were investigated. The Cu in PCBs leachate solution before and after metal removal process were quantified using flame atomic absorption spectrophotometer (FAAS). Result obtained showed that, the percentage removal of Cu was recorded to be higher at high adsorbent dosage which was 14.417% in 5 g dose and 11.219% in 1 g dose. Thus, it can be concluded that the higher the adsorbent dosage used, the greater the percentage removal of Cu metal.

Global distribution of sediment-hosted metals controlled by craton edge stability

Sustainable development and the transition to a clean-energy economy drives ever-increasing demand for base metals, substantially outstripping the discovery rate of new deposits and necessitating dramatic improvements in exploration success. Rifting of the continents has formed widespread sedimentary basins, some of which contain large quantities of copper, lead and zinc. Despite over a century of research, the geological structure responsible for the spatial distribution of such fertile regions remains enigmatic. Here, we use statistical tests to compare deposit locations with new maps of lithospheric thickness, which outline the base of tectonic plates. We find that 85% of sediment-hosted base metals, including all giant deposits (>10 megatonnes of metal), occur within 200 kilometres of the transition between thick and thin lithosphere. Rifting in this setting produces greater subsidence and lower basal heat flow, enlarging the depth extent of hydrothermal circulation available for forming giant deposits. Given that mineralization ages span the past two billion years, this observation implies long-term lithospheric edge stability and a genetic link between deep Earth processes and near-surface hydrothermal mineral systems. This discovery provides an unprecedented global framework for identifying fertile regions for targeted mineral exploration, reducing the search space for new deposits by two-thirds on this lithospheric thickness criterion alone. Major sediment-hosted base metal deposits are located within 200 km of the border between thick and thin lithosphere, according to statistical comparisons between global lithospheric thickness and known deposit locations.

Effect of Different Complexing Agent on Surface Morphology and Microstructure of Cu-Sn-Zn Coatings Electrodeposited From Less Hazardous Electrolyte

In the present work carbon was electrochemically coated with Cu-Sn-Zn ternary alloy coatings from an electrolyte containing copper chloride, tin chloride and zind chloride. The morphology and chemical composition of the deposits were examined by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The results exhibited that Cu-Sn-Zn coatings with 5,5-dimethylhydantoin as complexing agent contain a large amount of copper. It is found that sodium formate was the suitable complexing agents in production of Cu-Sn-Zn ternary alloy due to its uniform and smoothly depositions coated on substrate.

Experimental Studies on Chemical Activation of Cementitious Materials from Smelting Slag of Copper and Nickel Mine.

Gellable composite materials (GCM) were prepared from a smelting slag of copper and nickel deposits and cement, and activated using gypsum and chemical activators. The effects of material ratio, dosage of chemical activators, and gypsum on the mechanical properties of GCM were studied. Our results showed that the chemical activators of Na2SO4, Na2SiO3, NaOH, and Na2CO3 could improve the compressive strength of the GCM. Considering the market cost and ease operation, the compressive strength of the GCM could be significantly improved with 2% Na2SO4. The experiment results also showed that the compound chemical activator could improve the compressive strength of gelled material. The strength of GCM reaches 41.6 MPa when 2% gypsum and 80% of smelting slags of copper and nickel deposits were used, which met the national standards requirements of GCM. As such, it is expected that a large amount of copper and nickel mining smelting slag could be utilized for the production of cementitious materials.

Uptake of copper from acid mine drainage by the microalgae Nannochloropsis oculata.

The removal of heavy metals from acid mine drainage is a key factor for avoiding damage to the environment. The microalga Nannochloropsis oculata was cultured in an algal medium with 0.05, 0.1, 0.15, 0.2, and 0.25mM copper under completely defined conditions to assess its removal capacity; the effects of copper on the cell density and lipid productivity of N. oculata were also evaluated. The results showed that N. oculata was able to remove up to 99.92 ± 0.04% of the copper content in the culture medium. A total of 89.29 ± 1.92% was eliminated through metabolism, and 10.70 ± 1.92% was removed by adsorption. These findings are favorable because they indicate that a large amount of copper was extracted due to the ability of the microalga to metabolize copper ions. The cell density, growth rate, and lipid content decreased with increased concentrations of copper in the culture medium. A positive effect on the fatty acid profile was found, as the saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) content improved when the copper concentration was higher than 0.1mmolL-1, which can potentiate the production of high-quality biodiesel. N. oculata is a good option for the treatment of acid mine drainage due to its ability to eliminate a substantial percentage of the copper present. Moreover, combining different culture systems such that heavy metals are removed to non-toxic levels in the first stage and high cell densities, which promote lipid production, is obtained in the second stage would be an advantageous strategy.

Induction of cell cycle arrest and apoptosis by copper complex Cu(SBCM)2 towards oestrogen-receptor positive MCF-7 breast cancer cells.

Copper complexes have the potential to be developed as targeted therapy for cancer because cancer cells take up larger amounts of copper than normal cells. Copper complex Cu(SBCM)2 has been reported to induce cell cycle arrest and apoptosis towards triple-negative breast cancer cells. Nevertheless, its effect towards other breast cancer subtypes has not been explored. Therefore, the present study was conducted to investigate the effect of Cu(SBCM)2 towards oestrogen-receptor positive MCF-7 breast cancer cells. Growth inhibition of Cu(SBCM)2 towards MCF-7 and human non-cancerous MCF-10A breast cells was determined by MTT assay. Morphological changes of Cu(SBCM)2-treated-MCF-7 cells were observed under an inverted microscope. Annexin V/PI apoptosis assay and cell cycle analysis were evaluated by flow cytometry. The expression of wild-type p53 protein was evaluated by Western blot analysis. The intracellular ROS levels of MCF-7 treated with Cu(SBCM)2 were detected using DCFH-DA under a fluorescence microscope. The cells were then co-treated with Cu(SBCM)2 and antioxidants to evaluate the involvement of ROS in the cytotoxicity of Cu(SBCM)2. Docking studies of Cu(SBCM)2 with DNA, DNA topoisomerase I, and human ribonucleotide reductase were also performed. The growth of MCF-7 cells was inhibited by Cu(SBCM)2 in a dose-dependent manner with less toxicity towards MCF-10A cells. It was found that Cu(SBCM)2 induced G2/M cell cycle arrest and apoptosis in MCF-7 cells, possibly via a p53 pathway. Induction of intracellular ROS was not detected in MCF-7 cells. Interestingly, antioxidants enhance the cytotoxicity of Cu(SBCM)2 towards MCF-7 cells. DNA topoisomerase I may be the most likely target that accounts for the cytotoxicity of Cu(SBCM)2.

구리-L-리신 킬레이트의 Bacillus megaterium 내 축적

Copper is a bivalent mineral and nutritionally necessary for mammals. It has been used as an animal feed additive or growth factor for animals. However, large amount of copper contained in animal manure by oversupplying of copper have a negative impact on the soil environment. Chelates of copper and amino acids have the advantages of being better absorbed into the intestines than copper ions and less sensitive to photodegradation than amino acids. Bacillus spp., a sporeforming probiotic, have stability against heat and low pH and are used as animal growth factor or feed additives. In this study, copper-L-lysine chelate was accumulated in Bacillus megaterium ATCC 10778 to use as mineral-containing probiotics or feed additives. The highest chelation rate of copper sulfate and L-lysine was 62.53% after 1:1 reaction of copper sulfate to Llysine for 25 minutes at 70℃. FB media was selected for bioaccumulation of copper-L-lysine chelate in flask culture. In the fermentor culture, 38,043 ppm of copper ion was accumulated in 6.50×108 CFU/mL of B. megaterium.

Investigation of failure of steel steam generating evaporator tube involving delamination defects and corrosion

A low carbon steel tube burst at a coal powered power station (Orot-Rabin station, Hadera-Israel). The tube was composed of material specified to ASTM A210M-02 Gr. A1. The bursting of the tube caused a steam/water mix to escape through a hole during initial unit activation after maintenance repairs. The tube is a diagonal ribbed steam-generating tube, mainly used as a physical support for a superheater coil assembly. During internal visual inspection using a borescope, it was seen that a whole layer of metal had partially detached from the area around the hole, causing the tube wall to thin considerably prior to failure. Moreover, it was seen that the same area had undergone corrosion at an advanced stage. Optical metallography revealed that the metal layer had detached from the tube's internal surface due to a wide and thick two-dimensional delamination defect present beneath the internal surface, and that a large amount of copper was present near the detached layer's edge. Scanning Electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) verified the existence of an abnormal concentration of copper and zinc at the same location. This led to the final conclusion that the hole in the tube had formed due to a combination of a wide delamination defect left over from production, and severe galvanic corrosion enabling the defect's exposure and delamination, eventually causing wall thinning and failure.

Improving Gold (Bio)Leaching Efficiency Through Pretreatment Using Hydrogen Peroxide Assisted Sulfuric Acid

Compared to conventional recycling methods, the recovery of gold from electronic waste (e‐waste) using bioleaching is more environmentally friendly and sustainable. E‐wastes contain large amounts of copper that forms stable complexes with cyanide and competes with gold during bioleaching. To overcome this, e‐waste from printed circuit boards was pretreated with sulfuric acid and hydrogen peroxide to remove copper from the waste. The kinetics of the copper removal process was examined by varying sulfuric acid concentrations, hydrogen peroxide concentrations, e‐waste particle sizes, and temperature. Both sulfuric acid and hydrogen peroxide showed a significant effect on pretreatment; copper removal from the e‐waste was found to fit the diffusion‐controlled model. Under optimal pretreatment conditions (5 M H2SO4, 5 M H2O2, T = 313 K, and do = 50–75 μm, 85.5% of copper was removed from the e‐waste. Two‐step bioleaching (where e‐waste was added only after the bacteria has grown and produced significant lixiviant) and spent medium leaching (i.e., using cell‐free medium containing the lixiviant) were examined using the metabolically engineered Chromobacterium violaceum pBAD strain for extraction of gold from e‐waste. Spent medium leaching achieved a gold recovery of 36.4% as compared to 24.7% under two‐step bioleaching for pretreated e‐waste.