To date, biofilm and microbial communities for syngas and CO conversion to methane have been successfully established using various microbial inocula, including anaerobic digestion from biogas plants anaerobic sludge from wastewater treatment plants , anaerobic granular sludge , and mixtures of sludge with anaerobic granular sludge . Additionally, monocultures such as Methanosarcina barkeri in batch tests and co-cultures like mixed cultures of R. rubrum, M. barkeri, and M. formicicum have also been employed for CO and syngas biomethanation. However, it is challenging to determine how the source of inoculum may have influenced system performance in these studies, given the differences in reactor designs and operational conditions.