ABSTRACT
Introduction ................................................................................................................................ 114 Polymer Degrading Thermoactive Enzymes ............................................................................. 115
Cellulose Hydrolyzing Enzymes .................................................................................... 115 Endoglucanases .................................................................................................... 115 β-Glucosidases ..................................................................................................... 119
Xylanases ........................................................................................................................ 119 Starch Processing Enzymes ............................................................................................ 120
α-Amylases .......................................................................................................... 120 β-Amylases .......................................................................................................... 124 Glucoamylases ..................................................................................................... 124 α-Glucosidases .................................................................................................... 125 Pullulanases ......................................................................................................... 125 CGTases ............................................................................................................... 126 Branching Enzyme .............................................................................................. 126 Amylomaltases ..................................................................................................... 127
Pectin Degrading Enzymes ............................................................................................ 127 Chitinolytic Enzymes ..................................................................................................... 128 Proteases ......................................................................................................................... 129
Biocatalysis with Nonpolymeric Compounds ............................................................................ 132 Lipases and Esterases ..................................................................................................... 132 Alcohol Dehydrogenases ................................................................................................ 133 Glucose and Arabinose Isomerases ................................................................................ 134 C-C Bond Forming Enzymes ........................................................................................ 134 Nitrile-Degrading Enzymes ............................................................................................ 138
DNA Processing Enzymes ......................................................................................................... 138 Polymerase Chain Reaction ............................................................................................ 138 DNA Sequencing ............................................................................................................ 139 Ligase Chain Reaction .................................................................................................... 142
Chemical Products ..................................................................................................................... 142 Compatible Solutes ......................................................................................................... 143 Other Compounds ........................................................................................................... 143
Thermophiles as Cell Factories ................................................................................................. 145 Biomining ....................................................................................................................... 145
Lipids and Peptides ......................................................................................................... 145 Hydrogen Production ...................................................................................................... 146
Outlook ...................................................................................................................................... 146 References .................................................................................................................................. 147
Thermophilic archaea and bacteria that are able to grow at temperatures up to 110°C and at extremes of pH (thermoacidophiles and thermoalkaliphiles) are an interesting source of stable enzymes (extremozymes). These are in general superior to the traditional biocatalysts, because they provide proteins with unique properties and many show reasonable activity even at 120°C, at pH values between 0 and 3, pH 9 to 11 and in the presence of organic solvents (up to 99%). Aiming at the production of high-value products particularly for the chemical, pharmaceutical, cosmetic, food, feed, beverage, paper and textile industries, robust enzymes from thermophiles are gaining signi - cant interest. There is an increasing interest in the utilization of renewable sources to satisfy the exponentially growing energy needs. Therefore, ef cient enzyme systems are also needed for the breakdown of plant biomass, which contains complex substrates such a cellulose, hemicellulose, lignin, fats and oils. Microorganisms living in extreme habitats are an ideal source for polymer degraders, which allow to perform biotransformation reactions under nonconventional conditions under which many proteins are completely denatured. In this chapter a new generation of enzymes that are produced by thermophilic, thermoacidophilic and thermoalkaliphilic archaea and bacteria will be presented and their signi cance for industrial biotechnology will be highlighted.
