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

Abstract

A β-amylase-overproducing mutant of Clostridium thermosulfurogenes was grown in continuous culture on soluble starch to produce thermostable β-amylase. Enzyme productivity was reasonably stable over periods of weeks to months. The pH and temperature optima for β-amylase production were pH 6.0 and 60°C, respectively. Enzyme concentration was maximized by increasing biomass concentration by using high substrate concentrations and by maintaining a low growth rate. β-Amylase concentration reached 90 U ml −1 at a dilution rate of 0.07 h −1 in a 3% starch medium. A further increase in enzyme activity levels was limited by acetic acid inhibition of growth and low β-amylase productivity at low growth rates.