Endodextranase D8144 from Penicillium sp. (EC 3.2.1.2.) was immobilized on an epoxy-activated mono-lithic Convective Interaction Media (CIM®) disk in order to produce isomaltooligosaccharides (IMOS) fromDextran T40 in a continuous IMmobilized Enzymes Reactor (IMER). Enzymatic parameters and structureof IMOS were studied for free and immobilized enzymes. The immobilization efficiency of endodextranaseD8144 was about 15.9% (w/w) and the real specific activity was close to 6.5 U mg enz−1. The Km values(4.8 ± 0.2 g L−1) for free and immobilized enzymes were the same, showing the absence of diffusionallimitation. Moreover, specific patterns of DPs (Degrees of Polymerization) distributions were observedduring the enzymatic hydrolysis by HPAEC-PAD (High Pressure Anion Exchange Chromatography-PulsedAmperometric Detection). Thus, sought-after sizes of IMOS (DPs 8–10) were generated all over the hydrol-ysis. Finally, the results showed the high stability of this IMER since a relative enzymatic activity about78% was measured after 5400 volumes column.