PGM Spent Catalyst Bioleaching Consortium

Community ID CommunityMech:000049

Ecological State ENGINEERED

Environment contaminated soil
ENVO:00002874

An engineered acidophilic microbial consortium designed for sustainable recovery of platinum group metals (PGMs) from spent automotive catalysts and hydroprocessing catalysts. This bioleaching system employs a two-stage mechanism combining Acidithiobacillus thiooxidans for alumina support dissolution with biogenic thiosulfate producers for PGM complexation and mobilization. Spent three-way catalysts (TWC) from automotive exhaust systems contain precious metals (Pt, Pd, Rh) deposited on alumina (Al₂O₃) supports, while spent petroleum refinery hydroprocessing catalysts contain Pd, Ni, Mo, and Al. The consortium operates under acidic conditions in column bioreactors, achieving exceptional recovery rates: 93.2% Pd extraction, 82.9% Ni, 33.4% Al, and 22.7% Mo from spent petroleum catalysts. The bioleaching mechanism proceeds in two stages: (1) At. thiooxidans generates sulfuric acid that dissolves the alumina support matrix, exposing embedded PGM particles, and (2) biogenic thiosulfate (S₂O₃²⁻) produced during sulfur oxidation forms stable complexes with Pd and other PGMs in the presence of copper and ammonia, mobilizing them from the catalyst surface. The thiosulfate-copper-ammonia system enables selective PGM leaching without harsh cyanide reagents. This biotechnological approach offers an environmentally sustainable alternative to conventional pyrometallurgical PGM recovery (high-temperature smelting) and aggressive chemical leaching (aqua regia, cyanide), while addressing circular economy needs for critical materials recovery from automotive and industrial waste streams. The technology represents a significant advance in green metallurgy for spent catalyst recycling.

Taxonomy

Taxon	Ontology ID	Functional Roles	Abundance
Acidithiobacillus thiooxidans	NCBITaxon:930	PRIMARY_DEGRADER PRIMARY_PRODUCER	DOMINANT
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" doi:10.1016/j.jenvman.2019.04.081 - PARTIAL (IN_VITRO) "about 82.9% of Ni, 33.4% of Al, and 22.7% of Mo were leached after 315 h of column operation" PMID:38138568 - SUPPORT (IN_VITRO) "A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources." PMID:31059950 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
Acidithiobacillus ferrooxidans	NCBITaxon:920	PRIMARY_DEGRADER SYNTROPHIC_PARTNER	ABUNDANT
PMID:38138568 - SUPPORT (IN_VITRO) "A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources." doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
Sulfobacillus thermosulfidooxidans	NCBITaxon:28034	PRIMARY_DEGRADER SYNTROPHIC_PARTNER	COMMON
PMID:38138568 - SUPPORT (IN_VITRO) "A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources." doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "Among various operational modifications, submerged bioleaching in continuous mode was considered as the best strategy in which about 82.9% of Ni, 33.4% of Al, and 22.7% of Mo were leached after 315 h of column operation"
Thiobacillus thioparus	NCBITaxon:931	PRIMARY_PRODUCER	COMMON
PMID:31059950 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" PMID:38138568 - SUPPORT (IN_VITRO) "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"

Ecological Interactions

Taxon

Cross-feeding

Mutualism

Syntrophy

Competition

Commensalism

Niche partitioning

Colonization facilitation

Strain competition

Predation

Complementary Iron and Sulfur Oxidation

MUTUALISM

Source Taxon: Acidithiobacillus ferrooxidans

Target Taxon: Acidithiobacillus thiooxidans

Metabolites: iron(2+) (CHEBI:29033), iron(3+) (CHEBI:29034), sulfuric acid (CHEBI:26836)

Biological Processes:

oxidation-reduction process (GO:0055114)
sulfur compound metabolic process (GO:0006790)

Evidence

PMID:38138568 - SUPPORT (IN_VITRO)

"A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources."
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)

"The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"

Metal-Tolerant Sulfur Oxidation and Metabolic Redundancy

MUTUALISM

Source Taxon: Sulfobacillus thermosulfidooxidans

Target Taxon: Acidithiobacillus thiooxidans

Metabolites: palladium (CHEBI:26156), nickel(2+) (CHEBI:49786), sulfuric acid (CHEBI:26836)

Biological Processes:

response to metal ion (GO:0010038)
sulfur compound metabolic process (GO:0006790)

Evidence

PMID:38138568 - SUPPORT (IN_VITRO)

"A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources."
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)

"Among various operational modifications, submerged bioleaching in continuous mode was considered as the best strategy in which about 82.9% of Ni, 33.4% of Al, and 22.7% of Mo were leached after 315 h of column operation"

Alumina Support Matrix Dissolution

MUTUALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: sulfur (CHEBI:26833), sulfuric acid (CHEBI:26836), aluminium(3+) (CHEBI:28984), aluminium oxide (CHEBI:30073)

Biological Processes:

oxidation-reduction process (GO:0055114)
sulfur compound metabolic process (GO:0006790)

Downstream Effects:

→ Biogenic Thiosulfate-PGM Complexation

Evidence

PMID:38138568 - SUPPORT (IN_VITRO)

"Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)

"The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"

Biogenic Thiosulfate-PGM Complexation

COMMENSALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: thiosulfate (CHEBI:16094), palladium (CHEBI:26156), copper(2+) (CHEBI:29036), ammonia (CHEBI:16134), platinum atom (CHEBI:33364), rhodium atom (CHEBI:33359)

Biological Processes:

oxidation-reduction process (GO:0055114)
sulfur compound metabolic process (GO:0006790)

Evidence

doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)

"The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
PMID:31059950 - SUPPORT (IN_VITRO)

"The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
PMID:38138568 - SUPPORT (IN_VITRO)

"Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"

Column Bioreactor PGM Recovery

MUTUALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: palladium (CHEBI:26156), nickel(2+) (CHEBI:49786), molybdenum atom (CHEBI:28685), platinum atom (CHEBI:33364), rhodium atom (CHEBI:33359)

Biological Processes:

oxidation-reduction process (GO:0055114)

Evidence

doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)

"The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
PMID:38138568 - SUPPORT (IN_VITRO)

"Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"

Thiosulfate Metabolic Cycling

SYNTROPHY

Source Taxon: Acidithiobacillus thiooxidans

Target Taxon: Thiobacillus thioparus

Metabolites: thiosulfate (CHEBI:16094), sulfate (CHEBI:16189), sulfur (CHEBI:26833)

Biological Processes:

sulfur compound metabolic process (GO:0006790)
oxidation-reduction process (GO:0055114)

Evidence

PMID:31059950 - SUPPORT (IN_VITRO)

"The bacterial attachment study with FESEM indicated that the metal toxicity was induced on bacterial cells attached to the sulfur particles"
PMID:38138568 - SUPPORT (IN_VITRO)

"Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"

Environmental Factors

Factor	Value	Unit
pH for Alumina Dissolution	1.5-3.0	pH
PMID:38138568 - SUPPORT (IN_VITRO) "Based on these results, an optimization through an experimental design was performed, indicating the optimal conditions to be Na2S2O3 1.2 M, CuSO4 0.03 M, (NH4)2SO4 1.5 M, Na2SO3 0.2 M, pH 8, and 60 °C" doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "Different operational strategies such as submerged bioleaching in continuous mode, submerged bioleaching in resting period mode, free flow bioleaching in continuous mode, and free flow bioleaching in resting period mode were tested to find out the optimum bioleaching strategy for the recovery of metals from spent hydroprocessing catalyst"
Column Bioreactor Configuration	Continuous percolation	qualitative
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" PMID:38138568 - SUPPORT (IN_VITRO) "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Temperature	25-35	°C
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" PMID:38138568 - SUPPORT (IN_VITRO) "To optimize Pd bioleaching from a ground TWC, screening through a Plackett-Burman design determined that oxygen and temperature significantly affected the leaching yield negatively and positively, respectively"
PGM Recovery Efficiency	93.2% Pd, 82.9% Ni, 22.7% Mo	% extraction
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "Different operational strategies such as submerged bioleaching in continuous mode, submerged bioleaching in resting period mode, free flow bioleaching in continuous mode, and free flow bioleaching in resting period mode were tested to find out the optimum bioleaching strategy for the recovery of metals from spent hydroprocessing catalyst" PMID:38138568 - SUPPORT (IN_VITRO) "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Thiosulfate-Copper-Ammonia System	S₂O₃²⁻ + Cu²⁺/Cu⁺ + NH₃/NH₄⁺	qualitative
PMID:31059950 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" PMID:38138568 - SUPPORT (IN_VITRO) "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Substrate Type	Spent TWC and hydroprocessing catalysts	qualitative
doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO) "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported" PMID:38138568 - SUPPORT (IN_VITRO) "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"