Bioreactor silicone membrane

Fig. 23.4 Organophilic pervaporation (PV) for in situ recovery of volatile flavour compounds from bioreactors. The principle of PV can be viewed as a vacuum distillation across a polymeric barrier (membrane) dividing the liquid feed phase from the gaseous permeate phase. A highly aroma enriched permeate is recovered by freezing the target compounds out of the gas stream. As a typical silicone membrane, an asymmetric poly(octylsiloxane) (POMS) membrane is exemplarily depicted. Here, the selective barrier is a thin POMS layer on a polypropylene (PP)/poly(ether imide) (PEI) support material. Several investigations of PV for the recovery of different microbially produced flavours, e.g. 2-phenylethanol [119], benzaldehyde [264], 6-pentyl-a-pyrone [239], acetone/buta-nol/ethanol [265] and citronellol/geraniol/short-chain esters [266], have been published...

Attaway, H., Gooding, C. H. and Schmidt, M. G. 2001. Biodegradation of BTEX vapors in a silicone membrane bioreactor system. Journal of Industrial Microbiology and Biotechnology, 26,316-325. 

FIGURE 15 Design of a rotating wall vessel bioreactor. Cells are suspended in medium, which fills the vessel until no air bubble is left. Oxygen is delivered via a silicone membrane in the center of the vessel. The vessel rotates at a relatively low speed ( 30 rotations/min) to prevent settling of cells. 

The Tecnomouse (29) is a hollow fibre bioreactor containing up to five flat culture cassettes containing hollow fibres surrounded by a silicone membrane that gives uniform oxygenation and nutrient supply of the culture and ensures homogeneity within the culture. The system comprises a control imit (media supply), a gas and medium supply unit, and the five culture cassettes. 

Gas Permeable Membrane Aerator Bioreactor. This type of bioreactor has not yet been fully developed. Nevertheless, some information is available. For example, one bioreactor is equipped with an aerator composed of fine tubes made of polycarbonate, polypropylene, silicone gum, etc. This type of bioreactor should be valuable for immobilized plant cell cultures. 

Mori and Inaba (1990) applied a PV technique to attain both high productivity and efficient recovery of EtOH from a fermentation broth. The manbrane bioreactor consisted of a jar fermenter and a PV systan for the direct production of EtOH from uncooked starch with a thermophilic anaerobic bacterium, Clostridium thermohydrosulfuricum. From the four types of EtOH-selective monbranes tested, microporous PTFE membrane, the pores of which were impregnated with silicone rubber, was chosen for its large flux, high EtOH selectivity, and high stability. During... 

Based on the list of literature reviewed in this chapter, it can be pointed out that a comparatively limited number of studies on cell-immobilized membrane reactors (Table 20.3) and extractive membrane bioreactors (Table 20.8) have been conducted. Studies only from certain research groups who targeted a limited number of recalcitrant compounds (predominantly phenol) are available. Currently only a few publications on these topics are published each year. This obviously is an impediment to progress in their scale-up. Major hurdles for a commercial realization of EMBRs are the cost of silicone rubber membranes and other difficulties associated with the scaling up process. The development and implementation of these systems at an industrial scale requires a broader as well as in-depth understanding of the core processes. 

The miniPERM Bioreactor (30, 31) consists of two components, the production module (40 ml) containing the ceUs and the nutrient module (600 ml of medirrm). The modules are separated by a semi-permeable dialysis membrane (MWCO 12.5 kDa) which retains the cells and mAb in the production module but allows metabolic waste products to diffuse out to the nutrient module. There is a permeable silicone rubber membrane for oxygenation and gas exchange in the production module. The whole unit rotates (up to 40 r.p.m.) within a CO2 incubator. It can be purchased as a complete disposable ready to use unit or the nutrient module (polycarbonate) can be autoclaved and reused at least ten times. 

The hollow-fiber membrane bioreactor took the simple cylindrical geometry housing [dimension 13 mm inner diameter (ID) x 22 mm outer diameter (OD) x 40 mm L see Fig. 14.2]. Cellulose acetate hollow-fiber membranes [200 p,m ID, wall thickness of 14 p,m and molecular weight cutoff (MWCO) of 10 kDa] derived from hemodialysers used to construct the HFMBs. The hollow-fiber membranes were fixed in the bioreactor by using molded silicon rubber. The effective length of the fiber in the reactor was 30 mm with approximately 200 fibers in each bioreactor. The distance between adjacent fibers was approximately 400 p-m, of the order of the distance between natural blood capillaries in human bone. The volume external to the hollow fibers in each HFMB was approximately 3.5 mL, and this volume was available for the collagen gel together with the microcarriers with adherent cells. 

---