Scale-up of free flow electrophoresis: I. Purification of alcohol dehydrogenase from a crude yeast extract by zone electrophoresis

The potential and limitations in scaling-up free-flow electrophoresis, with emphasis on zone electrophoresis, are demonstrated. Purification of alcohol dehydrogenase (ADH) from a crude yeast extract was chosen as a model for an industrial approach to enzyme purification. In zone electrophoresis the separation quality strongly depends on the pH and conductivity of the background electrolyte, its residence time and flow rate, as well as the applied voltage. Optimization of these parameters resulted in a purification factor of 5.3 and a yield of 96% ADH, using a Tris/HCl buffer, pH 8.0, and a conductivity of 1 mS/cm, with a residence time of 10 min at 500 V. The loading capacity of the method for a laboratory-sized free-flow electrophoresis apparatus was limited to a sample throughput of about 0.4 g/h. By increasing the chamber dimensions it was possible to purify the enzyme by a purification factor of 4.7 and a yield of 93% ADH, at a throughput of about 1 g total protein/h. By simultaneously applying the sample at 3 input positions the throughput could be increased to 2.75 g/h with a purification factor of 4.7 and an overall yield of 90%.