Hyperthermophiles and their possible potential in biotechnology

To develop novel processes in microbial biotechnology organisms with outstanding properties are required. Archaea represent a nearly unexplored third domain ('continent') of life, which harbours organisms living in extreme environments such as alkaline to acidic hot springs, anaerobic sediments and highly saline environments. From high temperature terrestrial and marine biotopes many extreme heat-loving (hyperthermophilic) Archaea and Bacteria have been isolated, which grow at temperatures between 80 and 113 degrees C. Within the 16S rRNA-based phylogenetic tree of life, hyperthermophiles occupy the deepest phylogenetic branches representing more than 30 genera. In their mode to gain energy, they exhibit a great variety: obligate chemolithoautotrophs utilizing only CO2, hydrogen, and different sulfur compounds are primary producers in hot and anaerobic environments. Organotrophs grow on organic acids, alcohols, sugars, amino acids, or polymers like starch or chitin. This diversity in combination with their unusual heat resistance makes hyperthermophiles appropriate for new biotechnological applications at high temperatures. After cloning the genes into easy cultivable mesophiles, enzymes active at temperatures up to 130 degrees C are produced for food industry, biochemical and molecular research, or chemical industry. In addition, cultures can be applied directly in chemical processes like desulfurication of flue gases and in biohydrometallurgical processes. (C) 1998 Elsevier Science B.V. All rights reserved.