An immobilized two-enzyme system (fungal alpha-amylase/glucoamylase) and its use in the continuous production of high conversion maltose-containing corn syrups

Fungal alpha-amylase (E.C. 3.2.1.1) and glucoamylase (E.C. 3.2.1.3) were chemically attached to separate reactor modules made from Microporous Plastic Sheet (MPS). Immobilization of enzymes and subsequent chemical reactions were accomplished by pumping reactants through the sheet, i.e., perpendicular to the surface. The expressed activity of the reactor modules was ca. 800 U/g for both fungal alpha-amylase and glucoamylase. The kinetics and short-term effects of pH and temperature on the expressed activity of the immobilized enzymes were investigated. Using commercially available DE-42 corn syrup at 50% dissolved solids, half-lives of 2000 and 5000 h were achieved for glucoamylase and fungal alpha-amylase, respectively. The reactors were operated at 50 degrees C and at pH 4.3 for glucoamylase and 5.5 for fungal alpha-amylase. A typical DE-62 corn syrup product was continuously produced in a two-stage reactor system by pumping the feedstock through the glycoamylase reactor and then through the fungal alpha-amylase reactor. Saccharide distributions at each stage were controllable to +/-0.2%.