Biological product recovery steps

The complexity of biological processes generally requires many stages to produce a final, purified product from a particular composition of raw materials. Although a typical bioprocess consists of two main parts, upstream fermentation and downstream product recovery, it is not unusual to have between 10 and 20 steps in the overall process. This reflects the complex nature of a typical fermentation broth, which will consist of an aqueous mixture of cells, intracellular or extracellular products, unreacted substrates, and by-products of the fermentation process. From this mixture, the desired... 

The various steps in recovery of biological products from their natural environment have been divided into four categories.1 These are separation of solubles from insolubles, isolation, purification, and polishing. Separation of solubles from insolubles is a common chemical engineering operation and... 

After biological reactions have generated a product of interest, it is necessary to recover this product from a liquid mixture that typically contains several undesirable components. The treatment of any culture broth after bioreactor cultivation is known as downstream processing. Downstream processing can account for 60-80%) of the total production cost, particularly in the production of modern recombinant proteins and monoclonal antibodies. A typical downstream process requires several steps in the areas of solid-liquid separation, cell rupture, product recovery, and product purification. It is important to minimize the number of downstream processing steps required because significant product losses inevitably occur during each step.f ... 

Integrative protein recovery operations are supposed to tolerate particle-containing biological suspensions as initial feedstock and to deliver a clarified product concentrate which can be transferred to further purification steps. Ideally, a first fractionation of the protein matrix contained in the feed is performed as well, thus combining clarification, concentration, and capture in a single process step. 

The most important step of the inclusion body protein recovery scheme is the refolding of the denatured protein to form a biologically active product. Refolding can be relatively simple, for small monomeric proteins, or quite complicated when the protein consists of more than one polypeptide chains or contains several disulfide bonds. Difficult refolding processes can result in overall low recovery yields of active protein. This limits the use of inclusion body processes for the production of some recombinant products. 

Quantitative data should be obtained whenever possible. Identification of a product is only the first step in evaluating its significance. The quantity produced and its chemical and biological characteristics must be determined also. Lack of recovery data will leave the possibility that the major product was overlooked completely. 

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