Catalysis of Organic..

Lathouder, Kapteijn and Moulijn 395. Development of a Monolithic Bioreactor:Tailor-Made Functionalized CarriersAbstractKaren M. de Lathouder, Freek Kapteijn and Jacob A. MoulijnDelft University of Technology, Faculty of Applied Sciences, DelftChemTech,Section R&CE, Julianalaan 136, 2628 BL Delft, The Netherlandsk.m.delathouder@tnw.tudelft.nlThe use of a monolithic stirred reactor for carrying out enzyme-catalyzed reactions ispresented. Enzyme-loaded monoliths were employed as stirrer blades. The ceramicmonoliths were functionalized with conventional carrier materials; carbon, chitosan,and polyethylenimine (PEI). The different nature of the carriers with respect toporosity and surface chemistry allows tuning of the support for different enzymesand for use under specific conditions. The model reactions performed in this studydemonstrate the benefits of tuning the carrier material to both enzyme and reactionconditions. This is a must to successfully intensify biocatalytic processes. The resultsshow that the monolithic stirrer reactor can be effectively employed in both masstransfer limited and kinetically limited regimes.IntroductionCeramic honeycomb monoliths are porous macro-structured supports consisting ofparallel channels. On the walls a thin layer of active material can be applied (Figure1). Honeycomb catalyst supports were originally developed for use in automotiveemission control systems where the combination of lowpressure drop and high surface area are important (1).For liquid systems, the advantages of structured reactorscompared to fixed-bed or slurry reactors include a highavailable surface area, a low pressure drop over theFigure 1. Monolithsreactor, ease of product separation, absence ofmaldistribution problems, and easy scale-up (2,3).Immobilized enzymes have a wide range of practical applications. Although activityusually decreases slightly upon immobilization, they possess important advantagesover dissolved enzymes, of which the possibility to recover and reuse the enzyme isthe most important. Most conventional enzyme carriers are inorganic particles orporous beads of synthetic polymers or gel-like materials such as chitosan, agarose oralginate. If one uses large beads, intraparticle limitations are bound to occur (4).Note that in enzymatic systems, not only substrate diffusion can be limiting:intraparticle pH gradients or ionic strength gradients can be equally problematic. Analternative to large beads in a fixed-bed reactor is a stirred slurry of beads that can beas small as 100 μm (5). However, the soft support-material lacks the mechanical