In search of sulfate-reducing consortia able to degrade acetate under acidic conditions

Abstract

BACKGROUND: Sulfatereducing microorganisms (SRM) can help to remediate acidic effluents containing metals. One drawback of sulfate reduction is that some SRM do not oxidize completely the substrate to CO2 and acetic acid may remain as a byproduct, affecting the process efficiency. Acidic environments are a potential source of sulfatereducers able to thrive acidic conditions. This work aimed to develop cultivable consortia of sulfatereducing microorganisms able to consume acetate at acidic pH and analyze their community composition.

RESULTS Starting from sediment enrichments from a natural acidic source, by successive transfers and combinations of electron donors and pH we obtained seven sulfatereducing consortia. All the consortia consumed the acetate produced from the incomplete oxidation of the substrate (lactate or glycerol) and used 5375% of the reducing equivalents for sulfate reduction. The sulfide production rate of the consortia was between 0.220.26mmol/L·day in the range of pH 3 6, being slightly higher at acidic conditions (4 5). The microbial diversity of the consortia was dominated by 21 OTUs, including taxa of acetotrophic sulfate reducers (i.e., Desulfotomaculum and Desulfatirhabdium) and fermenting bacteria.

CONCLUSION The consortia reported here have the potential to serve as inoculum for sulfatereducing bioreactors and could help to overcome acetate accumulation at low pH.