Biooxidation of hydrogen sulfide to sulfur by moderate thermophilic acidophilic bacteria

The copper industry utilizes significant amounts of sulfuric acid in its processes, generating sulfate as waste. While sulfate-reducing bacteria can remove sulfate, it produces hydrogen sulfide (H₂S) as a byproduct. This study examined the capability of a consortium consisting of Sulfobacillus thermosulfidooxidans and Sulfobacillus acidophilus to partially oxidize H₂S to S° at a temperature of 45 °C. A fixed-bed bioreactor, with glass rings as support material and sodium thiosulfate as a model electron donor, was inoculated with the consortium. Formation of biofilms was crucial to maintain the bioreactor’s steady state, despite high flow rates. Afterward, the electron donor was changed to H₂S. When the bioreactor was operated continuously and with high aeration, H₂S was fully oxidized to SO₄²⁻. However, under conditions of low aeration and at a concentration of 0.26 g/L of H₂S, the consortium was able to oxidize H₂S to S° with a 13% yield. S° was discovered attached to the glass rings and jarosite. The results indicate that the consortium could oxidize H₂S to S° with a 13% yield under low aeration and at a concentration of 0.26 g/L of H₂S. The findings highlight the capability of a Sulfobacillus consortium to convert H₂S into S°, providing a potential solution for addressing environmental and safety issues associated with sulfate waste generated by the mining industry.