Current status of technical protein refolding

The expression of heterologous proteins in microbial hosts frequently leads to the formation of insoluble aggregates. To fully exploit the production capacity of the cells, efficient strategies for further processing have to be developed. While in lab scale matrix assisted refolding techniques, especially of histidine-tagged proteins have become very popular, in production scale refolding by dilution is still predominant due to its simplicity. However scaling up dilution processes leads to large volumes and low protein concentration. This is a heavy burden both for liquid handling and for subsequent downstream processing steps. Process development aims to operate at uniform, reproducible conditions, to reduce costs to a minimum and to guarantee the required quality of the product. The general refolding kinetics, exploration of appropriate refolding conditions are reviewed. The major refolding operations such as dilution, matrix assisted refolding, pressure driven refolding or continuous refolding applications are discussed in view of industrial applicability.