Hydrogen Sulphide Production at Alkaline, Neutral and Acid pH by a Bacterial Consortium Isolated from Peruvian Mine Tailing and Wetland

Abstract

The gol aim of this study is to optimize the ability to produce hydrogen sulphide (H2S) in pure and mixed cultures of sulfate reducing bacteria (SRB) at pH variations from 9 to 5. Hydrogen sulphide produced by SRB reacts with dissolved metals in water or tailings generating highly insoluble metal sulfides and therefore the selective immobilization of different metals. Three strains of SRB were isolated from Orcopampa mine tailings and from the Pantanos de Villa wetlands, both located in Peru. Cultures were identified by microscopy, cultural characteristics and biochemical tests as production of desulfoviridin and growth in different substrates. The production of H2S by pure and mixed cultures was evaluated at: acid pH (5), neutral pH (7) and alkaline pH (9). The mixed culture consisted of all three isolated species:Desulfobactersp. from mine tailings andDesulfovibrio desulfuricansandDesulfovibrio sapovorans from wetland sludges. Pure cultures of these three strains grew and produced H2S at both neutral or alkaline pH. At low pH no pure culture was able to grow and no production of H2S was detected. A mixed culture formed by the three isolated SRB was the only culture that grew and produced sulphide at the three different pH tested in shorter time (24 hours). The improvement of bacterial activity can be based in the metabolic diversity of the mixed culture able to use lactate and acetate as a result of the joint activity of these species. Energy obtained from the substrate is thus used more efficiently.