Thermoacidophilic Microorganisms and their Novel Biocatalysts

AbstractThermophilic acidophiles are microorganisms that are able to grow in pH and temperature ranges of 0.0–4.0 and 55–95 °C, respectively. Most of these microorganisms, which usually live in solfataric fields, belong to the archaea and include the genera Acidianus, Desulfurolobus, Metallosphaera, Stygiolobus, Sulfolobus, Sulfurisphaera, Sulfurococcus, Thermoplasma and Picrophilus. The sequencing of five complete genomes of thermoacidophilic organisms has allowed more detailed investigation regarding the evolution of organisms sharing extreme growth conditions of a unique niche, especially with respect to horizontal gene transfer. From such novel microorganisms, robust enzymes with potential biotechnological applications can be isolated. Enzymes that are optimally active at high temperature and extremely low pH are very rare and most of them are extracellular and involved in polymer degradation. Heat and acid stable α‐amylase, cyclomaltodextrinase (neopullulanase), maltose binding protein and endoglucanase have been purified and characterized from the thermoacidophilic bacterium Alicyclobacillus acidocaldarius. Archaeal glycosyl hydrolases have been characterized from Picrophilus torridus, Picrophilus oshima, Thermoplasma acidophilum and Sulfolobus solfataricus. Biotransformation reactions can be performed even at pH close to zero and temperatures of 100 °C.