Enzyme Complexes of Model Acetotrophic Methanogens

James G. Ferry, Principal Investigator

Pennsylvania State University

The conversion of renewable biomass to methane (biomethanation), an alternative to fossil fuels, requires several interacting groups of microorganisms which includes metabolically diverse methane-producing species (methanogens). Although diverse, all methanogens rely on the enzyme heterodisulfide reductase (Hdr). Remarkably, relatively little is known about the workings of Hdr which represents a significant shortfall in understanding the process of biomethanation necessary to exploit methods for improving the rate and reliability. Although a mechanism has been proposed for Hdr from an obligate CO₂-reducing methanogen, the research is hindered by the inability to produce variants to probe the role of active-site amino acids necessary to validate the proposal and further explore the mechanism. The research proposed in this application overcomes this barrier by investigating diverse Hdr enzymes for which variants are generated for greater comprehensive understanding. Furthermore, these more tractable Hdr enzymes derive from species producing methane from acetate which accounts for most of the methane produced in the biomethanation of renewable biomass. The results of this investigation are expected to provide a more complete understanding of methanogenesis applied to improving the biomethanation process.