Enhanced activity and tolerance of sulfide-oxidizing bacteria in a dual reactor haloalkaline biodesulfurization system

Aims Studies on haloalkaline biodesulfurization (BD) systems have depicted the process efficiency and active microbial community. This paper aims to unravel the functional potential of BD system’s microbial community by investigating its metabolic potential through molecular and kinetic approaches. Methods and results Biomass from all sections of a pilot dual-reactor BD system from six different operations was analysed using kinetic, molecular and genomic approaches. For kinetic analyses, at the end of six runs, biological oxidation (BO) rates of sulfide (0.1-2 mmol L−1), thiosulfate (0.1 to 32 mmol L−1), and biologically formed sulfur in the BD system (Bio-sulfur) (5 mmol L−1) were measured. Highest BO rates were ~ 0.38 µmol O2 mgN−1 sec−1 for sulfide at 1 mmol L−1-S HS− for the run with 0.9 g L−1 sulfide and 10 min HRT (Hydraulic retention time) in anoxic reactor and 0.064 µmol O2 mgN−1 sec−1 at 2 mmol L−1 S2O32−-S, for the run with 0.5 0.9 g L−1 sulfide and 10 min HRT in anoxic reactor, cDNA-based qPCR of sqr and fccB genes revealed association with sulfide oxidation efficiency and element sulfur formation. Function predictions via R-based functional prediction tool -Tax4Fun2 indicated a truncated Sox pathway of thiosulfate oxidation. Conclusions Higher sulfide concentrations boosted biological activity and increased tolerance within the active BD microbiome. Both FccAB and Sqr were prevalent, indicating their essential roles in sulfide oxidation. The predicted truncated Sox system suggests thiosulfate dismutation to sulfate and elemental sulfur.