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E-waste Bioleaching Consortium

Ecological State ENGINEERED
Environment contaminated soil
ENVO:00002874
Source File Ewaste_Bioleaching_Consortium.yaml

An engineered acidophilic microbial consortium adapted for recovering valuable metals from electronic waste, particularly printed circuit boards (PCBs). This consortium consists primarily of iron-oxidizing bacteria dominated by Leptospirillum ferriphilum with Sulfobacillus benefaciens, Acidithiobacillus ferrooxidans, and Acidithiobacillus thiooxidans contributing to metal solubilization. The community operates at extremely low pH (1.2 ± 0.1) and moderate temperature (35°C), oxidizing ferrous iron to generate ferric iron (Fe³⁺) that dissolves base metals (copper, zinc, nickel) and mobilizes precious metals (gold, silver, palladium) from PCB components. Metal recovery is exceptional: 100% copper dissolution (2.6-4.2 g/L), 100% zinc (303-543 mg/L), and 70% nickel (30-52 mg/L). However, PCB materials are toxic to the consortium, delaying the pre-oxidation phase from 11 days at 1% PCB load to 18 days at 2% load, with no growth above 8% PCB. Successive subculturing adapts the consortium to PCB toxicity, reducing lag phase by 2.6-fold. This biotechnological approach offers an environmentally-friendly alternative to pyrometallurgical e-waste processing (smelting), avoiding toxic emissions while recovering critical materials including copper for electrical applications and precious metals for electronics manufacturing. The two-step process may include subsequent cyanide-producing heterotrophs (Pseudomonas fluorescens, P. putida) for enhanced gold and silver extraction.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Leptospirillum ferriphilum NCBITaxon:178606
PRIMARY_PRODUCER PRIMARY_DEGRADER
DOMINANT
Sulfobacillus benefaciens NCBITaxon:453960
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
ABUNDANT
Acidithiobacillus ferrooxidans NCBITaxon:920
PRIMARY_PRODUCER PRIMARY_DEGRADER
ABUNDANT
Acidithiobacillus thiooxidans NCBITaxon:930
PRIMARY_DEGRADER
ABUNDANT
Acidithiobacillus ferrivorans NCBITaxon:160808
PRIMARY_DEGRADER
COMMON

Ecological Interactions

Ferrous Iron Oxidation for Metal Dissolution

CROSS_FEEDING

Source Taxon: Leptospirillum ferriphilum

Metabolites: Fe(II) (CHEBI:29033), Fe(III) (CHEBI:29034), copper(2+) (CHEBI:29036)

Biological Processes:

Downstream Effects:
→ Base and Precious Metal Solubilization

Evidence

  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "This study aimed to investigate the capacity of an acidophilic iron-oxidizing culture, mainly composed of Leptospirillum ferriphilum , to oxidize iron in PCB-enriched environments"
  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "Leptospirillum can potentially thrive in bioleaching environments as they have a greater capacity for iron oxidation activity than other FeOBs"

Base and Precious Metal Solubilization

MUTUALISM

Metabolites: copper(2+) (CHEBI:29036), zinc(2+) (CHEBI:29105), nickel(2+) (CHEBI:49786), gold atom (CHEBI:29287), silver atom (CHEBI:30512)

Biological Processes:

Evidence

  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "This study aimed to investigate the capacity of an acidophilic iron-oxidizing culture, mainly composed of Leptospirillum ferriphilum , to oxidize iron in PCB-enriched environments"
  • PMID:26704063 - SUPPORT (IN_VITRO)
    "An effective strategy for environmentally sound biological recovery of copper and gold from discarded printed circuit boards (PCB) in a two-step bioleaching process was experimented"

Sulfuric Acid Generation for pH Maintenance

MUTUALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: sulfur (CHEBI:26833), sulfuric acid (CHEBI:26836)

Biological Processes:

Evidence

  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "This study aimed to investigate the capacity of an acidophilic iron-oxidizing culture, mainly composed of Leptospirillum ferriphilum , to oxidize iron in PCB-enriched environments"

PCB Toxicity and Microbial Adaptation

COMPETITION

Metabolites: organic molecular entity (CHEBI:50860)

Biological Processes:

Evidence

  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "However, the inhibiting effect of PCBs limited the microbial activity by delaying the onset of the exponential iron oxidation"
  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "cultures showed no bacterial growth above 8% PCB equivalency"
  • doi:10.3389/fmicb.2021.669738 - SUPPORT (IN_VITRO)
    "Successive subculturing proved effective, reducing the pre-oxidation phase delay by up to 2.6 times"

Environmental Factors

Factor Value Unit
Extreme Acidity 1.2 ± 0.1 pH
Temperature 35 °C
Aeration with CO2 Enrichment 60 L/h with 1% CO2 L/h
PCB Pulp Density 1-8% (max 2% for growth) % w/v
Leaching Time 4-18 days