Amylases are a group of enzymes that hydrolyze starch, forming oligosaccharides, maltose or glucose. Amylases have applications in the industrial scale conversion of starch into glucose. For this, heat stable amylases are preferred since the saccharification reaction for the manufacture of glucose syrups can be done in large reactors between 70 and 80°C with a minimum threat of contamination by common microbes in the environment.
Starch is hydrolyzed by two main types of enzymes: an endo-acting a-amylase that produces maltooligosaccharides and an exo-acting glucoamylase that produces chiefly glucose. T. lanuginosus produces both enzymes that are fully stable at 50°C, though inactivated at 70°C (Mishra and Maheshwari, 1996). In the presence of calcium, a-amylase is nearly eight times more stable at 65°C. The a-amylase of T. lanuginosus is a dimer, which upon heating to the boiling temperature of water undergoes a structural reorganization and is progressively converted to an inactive trimeric species by the self-association of subunits.
The starch-degrading enzymes of T. lanuginosus are the most thermostable enzymes among fungal sources. The high purity of products (glucose and maltose) and their thermostability suggests the potential usefulness of T. lanuginosus glucoamylase and a-amylase in the enzymatic saccharification of starch.
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