Biotechnological application of microbial sulfidogenesis at haloalkaline conditions

Sulfide is a toxic and corrosive sulfur compound present in gas streams, like natural gas or biogas. Thus, before using the gas, sulfide can be removed using sustainable biodesulfurization technologies. These technologies use the natural ability of microbes to transform sulfide into elemental sulfur, which is not toxic and can be used in agriculture. However, in the current biodesulfurization technologies, sulfide is partly transformed into sulfate and thiosulfate which accumulate in the process and lead to higher caustic and water consumption. To prevent this higher caustic and water consumption, sulfate and thiosulfate can be transformed once again into sulfide which could be recycled back in the process. The major challenge is that this process operates at high pH and high salt concentrations which can be challenging for microbes present in most environments. The exception are soda lakes or soda soils where haloalkaliphilic microbes, microbes that live at high pH and high salt concentrations, thrive. In this project, we used sediments from soda lakes to inoculate bioreactors which allowed us to grow a microbial culture that can transform sulfate and thiosulfate into sulfide at high pH and salt concentrations. During this project, another interesting discovery was made about microbes that can produce formate in concentrations higher that organisms that live at neutral pH and low salt concentrations. Such microbes are also interesting to consider for new biotechnological applications.