Preparation of an immobilized two-enzyme system, beta-amylase-pullulanase, to an acrylic copolymer for the conversion of starch to copolymer for the conversion of starch to maltose. I. Preparation and stability of immobilized beta-amylase

β-Amylase (EC 3.2.1.2), obtained from barley, was chemically attached to a crosslinked copolymer of acrylamide-acrylic acid using a water-soluble carbodiimide. The derivative showed 23% β-amylase activity in relation to that of free enzyme with a coupling yield of 40% based on the amount of added β-amylase. In order to find optimal coupling conditions, the effect of pH and different carbodiimide concentrations was investigated. The enzymic activity associated with different β-amylase concentrations was further outlined. A slightly increased operational stability for the enzyme upon immobilization was observed. Markedly improved operational stability has been obtained by coupling in the presence of reduced glutathione of bovine serum albumin.