Biotechnology filtration operations

The first two categories, clarifying and crossflow filters, have been very well developed and optimized for use in biotechnology and standard wastewater treatment applications. Equipment is easily available for these applications, whether as small 0.2 micron sterilizing filter used to terminally sterilize 100 ml of product solution, or a small 500 ml crossflow filter used to concentrate a small amount of antibody solution. Many vendors of this equipment to wastewater treatment applications have their origins in the CPI (Chemical Process Industries), and have incorporated many of the scale-up and optimization properties developed in much larger units used in large scale chemical production. As a result, these two filtration unit operations are one of the most optimized and efficient used in wastewater treatment. 

The third category, cake filters, although well developed in many wastewater treatment applications, are the least developed of the filtration equipment use by the Biotech Industry. In the organic synthesis laboratory sometimes very simple equipment like a funnel and filter paper is used to accomplish this operation. Some other operations used for this filtration step in the lab are more sophisticated, but many are very labor intensive and limit the capacity of the overall production process itself. As a result, there is a need for optimization of the cake filtration equipment used in biotechnology. Cake filtration equipment is available in batch and continuous modes. Following are several examples of cake filtration units ... 

Filtration is a unit operation commonly employed nowadays in biotechnological processes. In this unit operation, a filter medium acts as a physical barrier to particles larger than its pores. Traditional filtration devices such as filter presses and rotary vacuum drum filters have so far found no application for the separation of animal cells. Nevertheless, membrane filters are commonly employed, as well as some alternative filter designs such as spin-filters. In the next sections, the most common types of filters used for animal cell separation will be discussed. 

Enzymatic reactions are commonly observed or practiced in various kinds of food and biotechnology products. With the goals of reducing operating costs and improving product quality, a number of enzyme immobilization techniques have been developed in recent decades [Woodward, 1985]. The availability of robust membranes, particularly porous inorganic membranes, has improved the enzyme immobilization technology. One type of membrane bioieactors immobilizes enzyme in the membrane pores by dead-end filtration of the enzyme solution. 

Nonuniform TMP values over the filtration surface area may cause substantial (up to 50%) reduction in the product recovery in the permeate. A novel approach to improving the flux and/or product recovery utilizes the concept of a uniform transmembrane pressure. lf This is achieved by varying the permeate side pressure with an independent recirculation pump to adjust the TMP to a constant value. A schematic of the UTP and conventional cross-flow configuration is shown in Figs. 11 and 12, respectively. The TMP profiles for the two operational modes are shown in Fig. 13. Flux improvements up to 500% have been achieved compared with the conventional cross-flow mode in many important food, beverage and biotechnology applications. 

Filtration is one of the commonest processes used, at all scales of operation, to separate suspended particles from a liquid, using a porous medium which retains the particles but allows the liquid to pass through. There is potentially a wide variety of filtration devices available for initial cell separation. However, the choice is restricted in biotechnology due to... 

---