Influence of different substrates on the production of a mutant thermostable glucoamylase in submerged fermentation.

Three mutations, Ser54→Pro, Thr314→Ala, and His415→Tyr, were identified in Aspergillus awamori glucoamylase gene expressed by Saccharomyces cerevisiae. The mutant glucoamylase (GA) was substantially more thermostable than a wild-type GA at 70 °C, with a 3.0 KJ mol(-1) increase in the free energy of thermo-inactivation.