The regulation of α-amylase production inBacillus licheniformis

Abstract

The production ofα-amylase (α-1,4 glucan-4-glucan hydrolase; E.C. 3.2.1.1.) by a strain ofBacillus licheniformis has been studied in batch and continuous cultures. The synthesis of this enzyme was shown to be repressed by glucose or other low-molecular-weight metabolisable sugars. Consequently, amylase production in a medium which contained “liquified” starch only began after the low-molecular-weight sugars had been dissimilated. Thereafter, the dextrins in the medium were degraded by amylase produced by the bacteria to yield further quantities of metabolisable sugars. These sugars were continuously dissimilated by the growing organisms and never accumulated to concentrations where they would repress further amylase synthesis. A clear analogy could thus be drawn with bacteria growing in a carbon-limited environment in a chemostat. Therefore,α-amylase production byB. licheniformis organisms growing in 3-litre chemostats was studied. No evidence was obtained to infer that an inducer was necessary for amylase production, and it was concluded that the prime factors influencing amylase production, in this species at least, were growth rate and catabolite repression.