Economics of bioseparations

Finally, more such studies must be carried out on real-life examples and made available in the literature. No doubt such studies are available in the different pharmaceutical industries, but due to economic and obvious reasons, they are restricted to only in-house circulation. This is an unfortunate aspect of the economics of bioseparation of different processes. Hopefully, people in the universities, at least, will pay more attention to this aspect, and fill this critical gap in the complete analysis of bioseparation processes. 

Sadana, A. Applications and economics of bioseparation. In Bioseparation of Proteins. Unfolding/ Folding and Validations, Satinder, A. Ed. Separation Science and Technology series Academic Press San Diego, 1998 Vol. 1,259-285. 

Sadana, A., Beelaram, A., Efficiency and economics of bioseparation, some case studies. Bioseparation 1994, 4, 221-235. 

In moving from laboratory- or pilot-scale processing to full-scale manufacturing, it can be difficult to scale up certain types of bioseparation equipment easily for example, high g centrifuges are available as bench-mounted units (using test tubes), but an equivalent industrial machine with a similar g force is unlikely to be a cost-effective solution, even if it were possible to build a suitable unit. It would not be realistic to consider 10 or 100 identical units as a realistic alternative. Compromises are therefore required as a process is commercialized, to ensure that the process remains technically and economically feasible. 

It is important to consider both the capital costs associated with designing, purchasing, and installing a piece of bioseparation equipment and the operating costs of maintenance utilities such as electricity, steam, and compressed air labor and any raw materials. In most cases, there will be a trade-off between capital and operating cost which may favor a particular type of equipment, depending on the desired initial capital investment and the economics of the process. 

The economic feasibility of a bioreaction process clearly depends on the characteristics of the associated bioseparation process, especially in the usual case when the product is present at low concentration in a complex mixture. For example, the existence of an extremely efficient and low-cost separation process for a particular compound could significantly lower the final concentration of that compound required in the bioreactor to achieve a satisfactory overall process. After noting that special approaches and processes are needed for efficient recovery of small molecules (ethanol, amino acids, antibiotics, etc.) from the dilute aqueous product streams of current bioreactors, I shall discuss further only separations of proteins. These are the primary products of the new biotechnology industry, and their purification hinges on the special properties of these biological macromolecules. 

The choice of a bioseparation technique will depend on a number of factors, including the initial location of the product inside or outside the cell, as well as the product size, charge, solubility, chemical or physical affinity to other materials, and so on. Economic factors also come into play, including the value of the product, the regulatory environment in which the product is manufactured, and the balance between the capital cost of the bioseparation equipment and the operating cost of running it. 

Chapter 16 provides guidance relating to the choice of industrial bioseparation equipment that is available and the issues that must be taken into account when selecting a suitable system to meet both technical and economic objectives. 

There are continuing efforts to develop cost-effective processes for fuel alcohol production, although the economics are often dependent on the availability of subsidized feedstocks to compete with traditional fuels derived from oil. The pretreatment and fermentation of such feedstocks, derived from corn, sugar cane, and even municipal waste, yields a dilute aqueous solution of ethanol which must be separated from a complex mixture of waste materials and then concentrated by distillation to remove water. Both batch and continuous production processes have been developed, with the requirement for effective bioseparations during both the pretreatment and ethanol recovery parts of the process. 

III. APPLICATIONS OF MODELS AND FLOW SHEETS IN BIOSEPARATION ECONOMICS... 

Liquid-liquid partitioning is a convenient and often economical method for bioseparations. L. Gu (personal communication, 1999) has shown that an acetonitrile-water system can be used for separation of proteins. This system partitions into two phases under subzero temperatures with the top phase containing more acetonitrile and water. The low temperature and the presence of water in both phases help reduce protein denaturation. An added advantage is that sample solution can be directly applied to reversed-phase high-performance liquid chromatography (HPLC) for further purification. Aqueous liquid-liquid partitioning is likely to remain an attractive choice for the separation of proteins, and exploration of new systems will continue. 

Displacement chromatography has an enormous potential as a preparative bioseparation technique. In many situations from the mg to the kg scale and beyond the displacement chromatography may theoretically be the most practical, the most economic and the most efficient approach to a given separation problem. However, in order to exploit the full potential of displacement chromatography, suitable displacer/stationary phase systems must become available. This chapter is intended as an introduction to our current understanding of the requirements for systematic displacer design. 

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