Scaleup of a fermentation for Methanobacterium thermoautotrophicum Delta-H: Characterization of the enzyme urease.

摘要

The subject of this study is the obligate anaerobe Methanobacterium thermoautotrophicum DeltaH. The product of this organism's respiration (the production of methane) is being investigated as an alternate energy source. It would provide a constant energy supply for hospitals in remote third world countries without a localized commercial energy supply.;For this reason, the metabolic pathways of Methanobacterium thermoautotrophicum DeltaH are under investigation. It is believed that this organism excretes urease, an enzyme that breaks down urea into carbon dioxide and ammonium. It is the fermentation of Methanobacterium thermoautotrophicum DeltaH and the preliminary identification of this enzyme, suspected to be urease, that is the ultimate goal of this study.;A successful fermentation process was developed which gave increased yields over the traditional culture bottle method. A few design parameters needed to be overcome to allow the available fermentor to be used as desired, these included media evaporation, stabilization of an anaerobic environment, and insulation. All these problems were overcome and the system proved to be satisfactory for fermentation. Sulfur sources were investigated and it was found that 0.07 mM cysteine & 0.8 mM sodium thiosulphate increased the growth rate and therefore decreased the time required for the fermentation. Another element found to decrease the time for a fermentation run was the addition of titanium (III) citrate, which eliminated the lag time associated with the adaptation of the cells. Finally, investigation into the "urease-like" enzyme present gave preliminary results which lead us to believe that both urease and adenosine deaminase are present, urease being the predominant enzyme.