Tubular membrane bioreactors for biotechnological processes
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MINI-REVIEW
Tubular membrane bioreactors for biotechnological processes Christoph Wolff & Sascha Beutel & Thomas Scheper
Received: 1 October 2012 / Revised: 23 November 2012 / Accepted: 23 November 2012 / Published online: 9 December 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract This article is an overview of bioreactors using tubular membranes such as hollow fibers or ceramic capillaries for cultivation processes. This diverse group of bioreactor is described here in regard to the membrane materials used, operational modes, and configurations. The typical advantages of this kind of system such as environments with low shear stress together with high cell densities and also disadvantages like poor oxygen supply are summed up. As the usage of tubular membrane bioreactors is not restricted to a certain organism, a brief overview of various applications covering nearly all types of cells from prokaryotic to eukaryotic cells is also given here. Keywords Tubular membranes . Bioreactor . Cultivation . Immobilization
Introduction Cultivation processes always need adequate bioreactor systems. The reactor design is determined by the needs of the cells, the process, and is based on a broad variety of reactor concepts. These range from classic stirred tank reactors over disposable bag reactors to membrane-based bioreactors. All of these reactors serve the same task: to provide an optimal environment for cells to grow and often to produce a certain product. Sometimes immobilization of the cultivated cells can be beneficial for cultivation. The cells are protected from shear C. Wolff : S. Beutel (*) : T. Scheper Institute for Technical Chemistry, Callinstr. 5, 30167 Hannover, Germany e-mail: [email protected]
stress caused by agitation or sparging. Slow growing cells can be cultivated in a perfusion mode without being washed out, and high cell densities can be maintained over a period of months. Various methods and techniques have been developed for cell immobilization (Belfort 1989). Typically, three approaches are used (Fig. 1). The most basic approach is the attachment or sorption of cells onto a surface (Fig. 1a). Biofilms are a typical example but also carrier beads in suspension are feasible. The entrapment of cells in porous matrices like hydrogels is also possible (Fig. 1b). Using membranes as barriers for cell immobilization is the third approach (Fig. 1c) for the immobilization of cells (Piret 1990). By using membranes for cell immobilization, the cells can attach to the surface; they are retained by the membrane pores while still submerse (filtration) or growing inside the pores. This review sums up the characteristics and applications of bioreactors using membranes to immobilize cells for cultivations.
Membrane-based bioreactors Membrane-based bioreactor (MBR) is the generic term for a large group of reactor types for an even larger field of applications. They all have in common a membrane that acts as a separation barrier to divide the reactor into two (or more) compartments. Membrane bioreac
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