Multi-Objective Optimization of Copper Bioleaching: Comparative Study of Pure and Co-Cultured Cultivation

Area of Science:

• Microbial biotechnology
• Hydrometallurgy
• Environmental science

Background:

• Bioleaching is a key process for recovering metals from low-grade sulfide minerals.
• Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans are crucial bacteria in metal bioleaching.
• Experimental design aids in optimizing microbial activity conditions efficiently.

Purpose of the Study:

• To optimize bioleaching conditions for indigenous iron- and sulfur-oxidizing bacteria from the Meydouk mine, Iran.
• To evaluate the performance of these bacteria in pure and mixed cultures in a semi-pilot operation.
• To characterize the isolated bacterial strains using 16S rRNA sequencing.

Main Methods:

• Bacterial DNA was extracted and 16S rRNA sequenced for species identification.
• Design-Expert software was used to optimize cultivation conditions.
• Copper recovery rates and oxidation-reduction potential (ORP) were monitored in percolation columns.

Main Results:

• 16S rRNA analysis confirmed both isolates belong to the Acidithiobacillus genus.
• Optimal conditions for Acidithiobacillus ferrooxidans: 35°C, pH 2.5, initial FeSO4 25 g/L.
• Optimal conditions for Acidithiobacillus thiooxidans: initial sulfur concentration of 35 g/L.
• Mixed cultures exhibited higher bioleaching efficiency than pure cultures.

Conclusions:

• A synergistic function between Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans enhances copper recovery rates.
• Optimized bioleaching conditions and the use of mixed cultures significantly improve metal recovery efficiency.
• Initial sulfur dosage and pre-acidification are effective strategies to boost metal recovery.