The biological leaching of metals from different waste streams by bacteria is intensively investigated to address metal recycling and circular economy goals. However, usually external addition of sulfuric acid is required to maintain the low pH optimum of the bacteria to ensure efficient leaching. Extremely acidophilic Acidithiobacillus spp. producing sulfuric acid and ferric iron have been investigated for several decades in the bioleaching of metal-containing ores. Their application has now been extended to the extraction of metals from artificial ores and other secondary sources. In this study, an optimized process for producing biogenic sulfuric acid from elemental sulfur by two sulfur-oxidizing species, A. thiooxidans and A. caldus and their combinations, was investigated in batch and stirred tank experiments. Using a combined culture of both species, 1.05 M and 1.4 M biogenic sulfuric acid was produced at 30 °C and 6% elemental sulfur in batch and semi continuous modes, respectively. The acid produced was then used to control the pH in a heap bioleaching system in which iron- and sulfur-oxidizing A. ferrooxidans was applied to biologically leach metals from waste incineration residuals. Metals like Cu, Ni, Al, Mn, and Zn were successfully recovered by 99, 93, 84, 77 and 68%, respectively within three weeks of heap bioleaching. Overall, a potential value recovery of incorporated metals >70% could be achieved. This highlights the potential and novelty of applying extremely acidophilic sulfur-oxidizing bacteria for cheap and efficient production of biogenic sulfuric acid and its use in pH control.

Department of Biochemistry Faculty of Science Masaryk University Kotlarska 2 61137 Brno Czech Republic

Department of Chemistry Faculty of Science Masaryk University Kotlarska 2 61137 Brno Czech Republic

University of Natural Resources and Life Sciences Vienna BOKU Department of Water Atmosphere Environment Institute of Waste Management Muthgasse 107 1190 Vienna Austria

University of Natural Resources and Life Sciences Vienna BOKU Dept of Agrobiotechnology IFA Tulln Inst of Environmental Biotechnology Konrad Lorenz Straße 20 3430 Tulln an der Donau Austria

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Proteomic Insights into the Adaptation of Acidithiobacillus ferridurans to Municipal Solid Waste Incineration Residues for Enhanced Bioleaching Efficiency