Mass Transfer of Hydrogen in a Culture of Methanobacterium Thermoautotrophicum Strain Hveragerdi

Abstract

Interspecies hydrogen transfer has been studied mostly in cultures maintained in closed vessels. In this way mass balances are obtained, but it is not possible to get information on the actual chemical environment in the vicinity of the cells. It is thus not surprising that apparent K_s values for hydrogen of 0.05 to 80 µM have been obtained for methanogens¹. These values are extremely high compared to the actual H₂ concentration observed in natural habitats (0.03 – 6 µM). H₂ concentrations in the headspace of the vessel are not a true indication of the conditions at the cell surface, the mass transfer from the gas phase into the cell being the limiting process. This situation seems similar to the one, which occured with CO₂ over ten years ago, when algae were cultured by bubbling the unstirred cell suspension with 5 –10% CO₂, resulting in a rather unreallistically high K_S value for CO₂ ².