Microbial Physiology of Alcohol and Hydrogen Production at High Temperatures

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Hyperthermophiles are a group of microorganisms growing optimally at 80°C and above. Some of them can ferment various kinds of biomass to produce alcohol and hydrogen, renewable energy sources. Due to their lower solubility in liquid phase at high temperatures, on-line collection of ethanol or butanol is advantageous compared to the use of a distillation step in a conventional fermentation process using yeast. Also, there would be no need for cooling, a significant energy consuming procedure required for most large-scale fermentation process. Hyperthermophiles also possess new thermostable enzymes that have great catalytic efficiency. Therefore, the long-term goal of the research described in this proposal is to isolate new and high alcohol- and hydrogen-producing hyperthermophilic microorganisms, characterize novel thermostable enzymes such as alcohol dehydrogenases, aldehyde-producing enzymes and hydrogenases, and reveal their roles in metabolic pathways and potential applications in the production of alcohols and hydrogen as biofuels. Key enzymes will be purified and characterized from newly isolated species and the representative hyperthermophiles already available from Bacteria (Thermotoga hypogea, Tmax=90°C and Thermotoga maritima, Tmax=90°C) and Archaea (Thermococcus guaymasensis, Tmax = 90°C and Hyperthermus butylicus, Tmax =112°C). Successful completion of this work will lead towards the construction of alternative and more efficient systems for the production of alcohol and hydrogen at higher temperatures, and the discovery of novel biocatalysts for applications in biotechnology.