Abstract

Amylases which produce maltotriose as the major end-product from starch are relatively rare. The thermophilic actinomycete, Thermomonospora fusca, produced an extracellular α-amylase which generated maltotriose as 61% of the identified products. The addition of maltotriose to a glucose-adapted exponential phase culture at 55°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°C, respectively, with an energy of activation of 59kJ/mol. The thermostability of the concentrated, washed amylase was increased by the presence of its starch reaction products, but not by added Ca2+.

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