Metal solubilization from metal-containing solid materials by cyanogenic Chromobacterium violaceum

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Cyanogenic bacteria produce hydrogen cyanide (HCN).
• HCN can form metal cyanides, which are water-soluble.
• Microbial metal mobilization is typically studied for gold recovery.

Purpose of the Study:

• To investigate the microbial mobilization of metals from solid materials using cyanogenic bacteria.
• To compare the efficiency of different bacterial strains in metal cyanide formation.
• To explore novel applications of microbial metal mobilization.

Main Methods:

• Cultivating cyanogenic bacterial strains (Chromobacterium violaceum, Pseudomonas fluorescens, Bacillus megaterium) with metal-containing solids (nickel powder, electronic scrap).
• Analyzing the formation of water-soluble metal cyanides.
• Identifying specific metal-cyanide complexes, such as tetracyanonickelate and dicyanaoaurate.

Main Results:

• All tested microorganisms formed water-soluble metal cyanides with varying efficiencies.
• Chromobacterium violaceum effectively mobilized nickel as tetracyanonickelate from nickel powder.
• Gold and copper were microbially solubilized as dicyanaoaurate and cyanide-complexed forms, respectively, from electronic waste.
• C. violaceum demonstrated higher efficiency in tetracyanonickelate formation compared to P. fluorescens and B. megaterium.

Conclusions:

• This study demonstrates the microbial mobilization of metals beyond gold from solid matrices.
• It highlights a novel mechanism of microbial metal mobilization based on bacterial cyanide production.
• The findings suggest potential industrial applications in biorecovery and bioremediation of metal-containing solids.