ABSTRACT
The modern biotechnology industry has provided the medical community with a new type of pharmaceutical, namely recombinant proteins and peptides. The number of such protein-based drugs is already impressive and expected to increase considerably in the future, as the function and gene sequence of more and more proteins is discovered, for example, as a result of the human genome project and related activities (genomics, proteomics). Soon gene therapy may bring about the next revolution in medical treatment, where for the first time it will be possible to correct the genetic causes of a disease rather than to just counter act the consequences of that genetic defect, i.e., the symptoms of the disease. Gene vaccines present another evolving medical possibility, which has been shown to have some significant advantages over the prophylactic measures taken at present against certain infectious diseases. Biopharmaceuticals, such as proteins and nucleic acids, thus extend the possibilities of medical treatment and thereby improve the quality of life. From an engineering point of view, however, the production and especially the purification of these biopharmaceuticals poses a considerable challenge.1 2
Proteins, i.e., the majority of the current biopharmaceuticals, are fragile, easily denatured substances. They are generally found in a complex environment such as cell, culture media or lysates (inclusion bodies). The concentration of the target molecule in the raw feed is often low, while extremely high final purities have to be reached in order to fulfill current legal requirements( see Table 3.1 for details). The production scale in the biopharmaceutical industry is often smaller than in the conventional pharmaceutical industry, i.e., in the kg/year rather than the t/year range. Speed (throughput) is another issue since prolonged exposure to a nonsterile environment or certain impurities (proteases) may lead to significant product degradation. Last but not least, the biotech industry, as any other, is governed by economic demands.3
