Intermittent energy storage mechanisms for sulphide oxidising bacteria

Summary

Sulphide oxidising bacteria (SOB) can remove sulphide from sulphidic waste streams in a so-called biodesulphurisation process. After sulphide is absorbed in a haloalkaline process solution it is converted by SOB to sulphur using oxygen as terminal electron acceptor. Interestingly, after exposing SOB to intermittent aerobic and anaerobic but sulphidic conditions SOB learn to remove sulphide even with delayed access to the terminal electron acceptor oxygen. It is hypothesised that SOB are able to store sulphidic compounds and/or electrons to bridge the gap between sulphide and oxygen. In this thesis, this “sulphide shuttling” behaviour of SOB is investigated by chemical and electrochemical techniques. SOB were found to remove sulphide in sequential steps including rapid chemical equilibria and slow enzymatic conversions. It is shown that aside from SOB also biosulphur and certain dissolved compounds are essential for rapid anaerobic sulfide removal. A sulphide shuttling pathway is postulated and the feasibility of an electrochemical biodesulphurisation setup is discussed.