Correlation of base consumption with the degree of hydrolysis in enzymic protein hydrolysis

It is fairly easy to control the enzyme hydrolysis of proteins in alkaline conditions by measuring the base consumption required to keel) the pH const ant in the reactor. Unfortunately, however, base consumption is not related in any simple way to the degree of hydrolysis reached at any given moment and to establish this relationship it is essential to find out the mean pK of the alpha -amino groups released during the hydrolytic process. We have shown here that the correct mean pK value varies according to the pH of the working conditions and that the relationship between these values may depe nd upon the kind of protein and protease used. We have put forward a method for determining this relationship experimentally by using a given protein- protease system, consisting of an alkaline titration of the raw protein and when partially hydrolysed. We have tested the results predicted by our the oretical model by applying it to the hydrolysis of whey proteins with a bac terial protease from Bacillus licheniformis at 50 degreesC. pH 8.0. This mo del can easily be applied to any hydrolytic process involving the appearanc e of functional groups that are partially protonizable under the working co nditions in question in order to follow the kinetics of the reaction via th e consumption of the neutralizing agent required to keep pH constant.