Amylolytic activity of Thermomonospora fusca

Amylases which produce maltotriose as the major end-product from starch are relatively rare. The thermophilic actinomycete, Thermomonospora fusca, produced an extracellular a-amylase which generated maltotriose as 61% of the identified products. The addition of maltotriose to a glucose-adapted exponential phase culture at 55 degrees C in mineral salts medium caused rapid induction of amylase biosynthesis. Addition of glucose to cells growing on starch did not repress amylase biosynthesis because the actinomycete had a marked preference for maltotriose over glucose. The pH and temperature optima for the amylase activity of concentrated, washed extracellular protein were 6.0 and 65 degrees C, respectively, with an energy of activation of 59 kJ/mol. The thermostability of the concentrated, washed amylase was increased by the presence of its starch reaction products, but not by added Ca2+.