Control of an affinity purification procedure using a thermal biosensor

Lactate dehydrogenase (LDH) was recovered from a solution by affinity binding to an N 6 ‐(6‐aminohexyl)‐AMP‐Sepharose gel. An enzyme thermistor unit was employed to continously measure the activity of the unbound LDH. The enzyme activity signal from the enzyme thermistor was used in a PID controller to regulate the addition of AMP‐Sepharose gel to the LDH solution. In another type of experiment, a desktop computer was utilized to control the addition of the adsorbent. Both systems worked satisfactorily, and enabled a rapid and accurate assessment of correct addition of adsorbent.