Enrichment of mesophilic syngas-converting consortia for methane production

The use of waste biomass as raw material for syngas production has emerged as a sustainable and cost-effective alternative to the conventional gasifiable feedstock. In addition, syngas bioconversion into value-added compounds could be an interesting approach for carbon fixation and syngas valorization, but some limitations must be overcome. One of the most important issues is to establish a robust microbial culture able to use CO as a carbon source. In the present study, an anaerobic consortium was enriched with a synthetic syngas mixture with a composition similar to that obtained from biomass gasification. Four syngas dilutions (25, 50, 75 and 100%) were tested to determine the CO tolerance of the mixed culture and evaluate its growth kinetics. The results showed the successful enrichment of a mesophilic syngas-converting consortium able to thrive in concentrations up to 30% CO. Volatile fatty acids (mostly acetate) and CH4 were the main products of its metabolism, reaching up to 54.27±1.04 mM of VFAs concentration and a CH4 production of 15.41±0.15 mmol·d-1. The accumulation of organic acids in the liquid phase appeared as a key factor for the development of the community, triggering its inhibition.