| Abstrakt: |
Microorganisms play an essential role in the global carbon budget with methanogenesis being a significant global source of methane. The ability to produce hydrocarbons other than methane is widespread among microorganisms and the diversity of hydrocarbon structures that are made is remarkable. However, other than microbial methane production, we know very little about the biochemical processes involved in microbial hydrocarbon formation. Methane production from natural polymers involves a consortium of interacting microbial species. Gibbs free energy yields associated with methanogenesis depend significantly on environmental conditions, especially temperature, activities (concentrations) of substrates and products, and pH, and are typically substantially smaller in natural systems than in growth-optimized cultures. The Gibbs free energy changes involved in the conversion of hydrocarbons, fatty and aromatic acids, alcohols, and hydrogen to methane are close to thermodynamic equilibrium. The low Gibbs free energy changes by which methanogenic consortia operate imply the existence of a minimum free energy change needed to sustain microbial growth, e.g., a biological energy quantum (BEQ), which is support both by theoretical considerations and experimental data. Methanogenic consortia provide excellent models to study interspecies interactions and highly efficient energy economies. [ABSTRACT FROM AUTHOR] |
