Conventional enzyme membrane reactors are not appropriate for a continuous synthesis of macromols. and simultaneous product release. By immobilizing the enzyme in sufficiently large pores of a membrane an ensemble of miniaturized bioreactors is created. Product mols. are continuously removed from the enzyme by the flow of the reaction mixt. across the membrane. Addnl., by varying the flow rate, it ought to be possible to influence the substrate as well as the enzyme-product residence times and thereby the product macromol.'s size. In this paper we present the first results of expts. involving enzymic 1,4-a-glucan synthesis, using sucrose as substrate, maltooligosaccharides (DP 3-6) as primers, and membrane-immobilized amylosucrase. Epoxy groups for a covalent enzyme immobilization were generated on polypropylene microfiltration membranes by heterogeneous photoinitiated graft polymn. of glycidyl methacrylate. The influence of primer concn. and flow rate through the enzyme-membrane on amylosucrase activity, mol. growth, and coupling efficiency for glucose (% of coupled glucose vs. free glucose) were investigated. The enzymically mediated chain elongation of maltooligosaccharides by the successive addn. of glucose units was achieved for the first time in a transmembrane process utilizing amylosucrase membranes.