Continuous Production of Thermostable beta-Amylase with Clostridium thermosulfurogenes: Effect of Culture Conditions and Metabolite Levels on Enzyme Synthesis and Activity.

A beta-amylase-overproducing mutant of Clostridium thermosulfurogenes was grown in continuous culture on soluble starch to produce thermostable beta-amylase. Enzyme productivity was reasonably stable over periods of weeks to months. The pH and temperature optima for beta-amylase production were pH 6.0 and 60 degrees C, respectively. Enzyme concentration was maximized by increasing biomass concentration by using high substrate concentrations and by maintaining a low growth rate. beta-Amylase concentration reached 90 U ml at a dilution rate of 0.07 h in a 3% starch medium. A further increase in enzyme activity levels was limited by acetic acid inhibition of growth and low beta-amylase productivity at low growth rates.