Sulfide removal from livestock biogas by Azospirillum-like anaerobic phototrophic bacteria consortium

• Biodegradation of livestock produces valuable biometane but also corrosive sulfides.
• Sulfide was removed by anaerobic phototrophic bacteria consortium from swine waste.
• A newly Azospirillum-like bacteria was reported.

Biogas production from anaerobic biodegradation of livestock waste is a potential source of renewable energy. In addition to methane, biodegradation of this high-strength waste also produces sulfide that must be removed in order to prevent costly corrosive impacts on infrastructure. In this work, an anaerobic, phototrophic microbial community enriched from the native population in a swine waste lagoon was evaluated for its potential to remove sulfide from swine waste biogas. Batch experiments with the consortium attained removal efficiencies greater than 97% for sulfide concentrations above 1200 ppm. 16S rRNA gene sequencing revealed that the dominant population was most closely related to the isolate Azospirillum strain C5 (similarity index of 99%). Photomicrograph of the enriched consortium revealed the presence of cells with intracellular globules resembling sulfur storage. The enrichment of Azospirillum-like and the concomitant sulfide consumption suggest that this microorganism played an important role in sulfide removal in the bioreactor.