Sulfur Reduction in Acid Rock Drainage Environments

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Acidic environments, common in mining and industrial waste, pose challenges for metal recovery.
• Sulfur reduction is a potential biological process for metal recovery from these challenging environments.

Purpose of the Study:

• To explore the microbiological suitability of acidophilic sulfur reduction for metal recovery.
• To isolate and characterize acidophilic sulfur-reducing bacteria from acidic sediments.

Main Methods:

• Enrichment of sulfur reducers from acidic sediments at varying pH (2-5) using different electron donors.
• Isolation and characterization of dominant bacterial strains, including 16S rRNA gene sequencing.
• Testing of isolated strain's growth range, metal tolerance, and optimal sulfur source.

Main Results:

• Highest sulfide levels were observed at pH 3 (hydrogen) and pH 4 (acetate).
• An acidophilic strain, TR1, belonging to the Desulfurella genus, was isolated and demonstrated broad pH (3-7) and temperature (20-50 °C) tolerance.
• Strain TR1 exhibited significant tolerance to lead (Pb2+) and nickel (Ni2+), with maximal tolerated concentrations of 0.09 mM and 0.03 mM, respectively.
• Biosulfur was the most effective sulfur source for rapid growth, with a doubling time of 1.9 days.

Conclusions:

• The isolated acidophilic sulfur-reducing bacterium, strain TR1, is a promising candidate for biotechnological applications.
• Strain TR1's tolerance to low pH and high metal concentrations makes it suitable for treating metal-laden acidic streams.
• This research supports the use of microbial sulfur reduction for efficient metal recovery from industrial waste.