An engineered acidophilic microbial consortium specifically designed for recovering gallium from waste light-emitting diodes (LEDs) through non-contact bioleaching. This mixed community consists of three iron- and sulfur-oxidizing bacteria in equal proportions (1:1:1 ratio): Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, and Leptospirillum ferrooxidans. The consortium produces biogenic lixiviants - primarily sulfuric acid (H₂SO₄) from sulfur oxidation and ferric iron (Fe³⁺) from iron oxidation - that solubilize gallium from GaN-based LED materials without direct contact between microbes and solid waste. Operating at pH 1.0-1.5 and 15 g/L pulp density, the system achieves exceptional 99.5% gallium leaching efficiency within just 3 days. The non-contact bioleaching approach separates the bioreactor (where microbes generate lixiviants) from the leaching reactor (where acids attack LED waste), preventing microbial inhibition by toxic LED components while enabling gallium recovery. In addition to gallium, the process recovers copper and nickel from LED substrates and interconnects. This biotechnological platform offers a sustainable alternative to harsh chemical leaching methods, utilizing microbial metabolism to extract critical materials from electronic waste while avoiding toxic emissions and reducing environmental impact.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
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| Acidithiobacillus thiooxidans | NCBITaxon:930 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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ABUNDANT |
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| Acidithiobacillus ferrooxidans | NCBITaxon:920 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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ABUNDANT |
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| Leptospirillum ferrooxidans | NCBITaxon:180 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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ABUNDANT |
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Ecological Interactions
The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.
Biogenic Sulfuric Acid Production for Gallium Leaching
PARTIAL - The existing 2025 source excerpt attributes sulfuric-acid generation from elemental sulfur to A. thiooxidans in the mixed culture, lowering pH to 1.53. Acid is a reported contributor to gallium leaching, not demonstrated mutualism or a complete member-specific leaching yield. The selected excerpt is retained with provenance limits because the full primary Results was unavailable in this review; unbalanced GaN chemistry and continuous-production claims are not retained.
Participating Taxa: Acidithiobacillus thiooxidans
Metabolites: sulfuric acid (CHEBI:26836 · MediaIngredientMech · CMMMech)
Biological Processes:
- sulfur compound metabolic process (GO:0006790 · PathwayMech)
PARTIAL - Sulfur oxidation supplies the acid component of the mixed-culture lixiviant. The selected 2025 excerpt supports this production role, not a quantified cooperative effect or independently verified member-removal experiment in the unavailable full Methods.
Evidence
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doi:10.1016/j.jece.2025.120403 - PARTIAL (IN_VITRO)"A. thiooxidans in the mixed bacterial community oxidizes the elemental sulfur to generate sulfuric acid, thereby decreasing the pH to 1.53."
Ferric Iron Generation in the Mixed Consortium
PARTIAL - Existing 2025 source excerpts identify A. ferrooxidans and L. ferrooxidans as producers of ferric ions from ferrous iron in the mixed community. This supports a joint iron-oxidizing guild contribution, not experimentally resolved pH niche partition, mutual benefit or relative member contributions. The 4-5 g/L stepwise ferric condition in PMID31203122 belongs to a separate adapted A. ferrooxidans system and is not an exact-consortium result.
Participating Taxa: Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans
Metabolites: Fe(II) (CHEBI:29033 · MediaIngredientMech · CMMMech), Fe(III) (CHEBI:29034 · MediaIngredientMech · CMMMech)
PARTIAL - Iron oxidation supplies ferric ions as the oxidizing component of the mixed-culture lixiviant. This component relationship is retained from the 2025 excerpts; the separate 2019 single-strain ferric-dosing experiment does not establish its magnitude or guild dependence here.
Evidence
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doi:10.1016/j.jece.2025.120403 - PARTIAL (IN_VITRO)"In the mixed microbial community, iron-oxidizing bacteria (A. ferrooxidans and L. ferrooxidans) oxidized Fe(II) to generate Fe(III) ions."
Mixed-Consortium Lixiviant Production
PARTIAL - The consortium assembled at an A. thiooxidans:A. ferrooxidans:L. ferrooxidans ratio of 1:1:1 produces a biogenic lixiviant containing sulfuric acid and ferric ions. The source excerpt reports both components contribute to gallium extraction. Joint contribution is not by itself evidence of synergy, optimized inoculum ratio, persistent equal abundance or pH-partitioned coexistence. Selective component and member controls remain to be checked against the complete primary source.
Participating Taxa: Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans
Metabolites: sulfuric acid (CHEBI:26836 · MediaIngredientMech · CMMMech), Fe(III) (CHEBI:29034 · MediaIngredientMech · CMMMech)
Biological Processes:
- sulfur compound metabolic process (GO:0006790 · PathwayMech)
Biogenic lixiviants produced by the mixed culture enable the non-contact gallium leaching endpoint reported for 15 g/L waste LEDs over 3 days. The primary abstract directly supports this functional production-to-recovery connection; it does not quantify separate acid/ferric contributions or demonstrate mutual benefit among the producing organisms.
Evidence
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doi:10.1016/j.jece.2025.120403 - PARTIAL (IN_VITRO)"Both sulfuric acid and ferric ions in the bioleaching agent contribute to gallium extraction from WLEDs"
Non-Contact Gallium Recovery
The mixed-community biogenic lixiviant achieved 99.5% gallium leaching at 15 g/L waste LEDs in 3 days under non-contact conditions, compared with 45.59% during contact bioleaching. This is a positive engineered community output, not a commensal interaction or proof of continuous lixiviant recycling. The primary abstract also reports contact-associated gallium adsorption up to 21.43% and proposes a role for bound extracellular polymers; the component-specific adsorption mechanism and its contribution to the recovery difference remain unresolved.
Participating Taxa: Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans
Metabolites: sulfuric acid (CHEBI:26836 · MediaIngredientMech · CMMMech), Fe(III) (CHEBI:29034 · MediaIngredientMech · CMMMech), gallium(3+) (CHEBI:84043 · MediaIngredientMech · CMMMech)
Evidence
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doi:10.1016/j.jece.2025.120403 - SUPPORT (IN_VITRO)"The biogenic lixiviants achieved a Ga leaching efficiency of 99.5 % in 15 g/L pulp density during 3 days of non-contact bioleaching."
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How do individual lixiviant components and B-EPS adsorption control the contact/non-contact gallium difference?
Preserve the 2025 mixed-community recovery comparison, but keep it separate from the adapted single-strain A. ferrooxidans experiment in PMID31203122 at20 g/L. Selected cached 2025 excerpts retain acid/iron roles with PARTIAL support; content_type:full is not proof that complete Methods were read. Publisher access returned403. The abstract reports Ga adsorption up to21.43% and hypothesizes protein/polysaccharide roles; this does not isolate their contribution to the recovery gap or close a total-Ga balance. Obtain authorized primary Methods and evaluate a distinct adsorption node/edge through the one-record Edison workflow before extending the graph. No paid run or new structure is included here.
Attaches to: ecological_interactions#Biogenic Sulfuric Acid Production for Gallium Leaching, ecological_interactions#Ferric Iron Generation in the Mixed Consortium, ecological_interactions#Mixed-Consortium Lixiviant Production, ecological_interactions#Non-Contact Gallium Recovery
Environmental Factors
| Factor | Value | Unit |
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| Extreme Acidity for Gallium Dissolution | 1.0-1.5 | pH |
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| LED Waste Pulp Density | 15 | g/L |
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| Rapid Leaching Duration | 3 | days |
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Growth Media
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