Syngas fermentation to biofuels: Effects of hydrogen partial pressure on hydrogenase efficiency

Producing biofuels from gasified biomass (synthesis gas) via microbial fermentation is currently being pursued as one alternative in biofuels development. In synthesis gas fermentation, reducing equivalents from H₂ oxidation via hydrogenase is important towards directing more carbon towards product formation. In this work, kinetic studies of H₂ utilization via the Clostridium P11 hydrogenase enzyme were performed to determine the most appropriate model to predict hydrogenase activity as a function of H₂ partial pressure. An important aspect of this work included the proper analysis of electron acceptors used in the kinetic studies. The KH2 model parameter governing the effect of H₂ partial pressure on activity was ~30kPa (absolute), independent of the type and concentration of electron acceptor. The KH2 value indicates that H₂ partial pressures typically associated with syngas fermentation will result in compromised efficiency of the hydrogenase activity.