Microbiological analysis of the population of extremely haloalkaliphilic sulfur-oxidizing bacteria dominating in lab-scale sulfide-removing bioreactors

Thiopaq biotechnology for partial sulfide oxidation to elemental sulfur is an efficient way to remove H2S from biogases. However, its application for high-pressure natural gas desulfurization needs upgrading. Particularly, an increase in alkalinity of the scrubbing liquid is required. Therefore, the feasibility of sulfide oxidation into elemental sulfur under oxygen limitation was tested at extremely haloalkaline conditions in lab-scale bioreactors using mix sediments from hypersaline soda lakes as inoculum. The microbiological analysis, both culture dependent and independent, of the successfully operating bioreactors revealed a domination of obligately chemolithoautotrophic and extremely haloalkaliphilic sulfur-oxidizing bacteria belonging to the genus Thioalkalivibrio. Two subgroups were recognized among the isolates. The subgroup enriched from the reactors operating at pH 10 clustered with Thioalkalivibrio jannaschii-Thioalkalivibrio versutus core group of the genus Thioalkalivibrio. Another subgroup, obtained mostly with sulfide as substrate and at lower pH, belonged to the cluster of facultatively alkaliphilic Thioalkalivibrio halophilus. Overall, the results clearly indicate a large potential of the genus Thiolalkalivibrio to efficiently oxidize sulfide at extremely haloalkaline conditions, which makes it suitable for application in the natural gas desulfurization.