Production of protein hydrolysates in an enzymatic membrane reactor

The hydrolysis of casein in the presence of proteolytic enzymes: thermolysin and subtilisin, is discussed. For both biocatalysts an appropriate process temperature was chosen and the kind and values of constants in the kinetic equation were determined. Thermolysin was selected for further studies as the more appropriate catalyst because of a strong inhibition of subtilisin.A model of the process was proposed for enzymatic reaction which takes place in a membrane bioreactor with a complete retention of the enzyme and a partial retention of the substrate in the reaction zone. Having selected a proper membrane, the model was successfully verified using the data from the considered casein hydrolysis. It was proved that at a relatively high substrate retention (i.e. ca. 50%), the substrate conversion degree could increase by ca. 50%. Owing to a high cost of biocatalysts such process intensification is significant. It is all the more promising, as separation of the enzyme on a membrane allows us to use the biocatalyst many times without applying any surface immobilisation techniques.