Synergetic alginate conversion by a microbial consortium of hydrolytic bacteria and methanogens

Sludge, of which alginate-like biomaterial is a major organic component, is an increasing environmental problem. Thus, efficient anaerobic degradation of alginate provides a new method for sludge utilization. In this study, anaerobic alginate hydrolytic bacteria (AHB) were proposed to enrich with methanogens synergetically to reduce the inhibition of intermediate metabolites. The COD of produced methane reached 80.7 ± 1.9% (n = 4) of initial alginate COD. After considering the microbial growth (8%-18% of COD), a good COD balance indicated that alginate was fully consumed and the main final metabolites were methane and CO₂. Methanogenesis could promote alginate conversion by AHB. The enriched bacteria for alginate degradation in this study were different from that of former known AHB. The metabolic pathway of alginate degradation was revealed by metagenomics, in which oligo-alginate lyase was detected in twelve bacteria, and typical carbon metabolic pathways to convert alginate to methane were identified. More studies of bacterial isolation and biofuel production are still needed in the future.