Degradation of ribonucleic acid by immobilized ribonuclease

An immobilized enzyme (pancreatic ribonuclease bound to porous titania) was investigated for the degradation of purified yeast ribonucleic acid as a substrate. The immobilized enzyme is active and stable in the pH range 4--8. Dependence of enzymatic activity on ionic strength, pH, temperature, fluid flow rate, and substrate concentration were investigated. A cumulative fluid residence time of 6 sec is sufficient for 50% substrate conversion at 25 degrees C and pH 7.0. The critical flow rate (i.e., the fluid flow rate necessary to remove film diffusion resistance) approximately doubles with each 10 degree C rise in reaction temperature. The critical flow rates obtained in this study are about 40 times greater than those obtained for a similar study on immobilized glucose oxidase. Arrhenius plots gave activation energies of -9.6 and -7.1 kcal/g mol at pH 4.6 and 7.0, respectively. The work reported herein is a bench-scale investigation of an immobilized enzyme with primary emphasis on the mass transfer and kinetic characteristics of the system. The rapid reaction rates obtainable at relatively low temperatures offer a potential alternative method of purifying yeast single cell protein (SCP) with miminum loss of desired protein. The key questions are how such a system would react in a yeast homogenate, what conditions in such a system must be controlled, and what type of immobilized reactor should be utilized, if such further work continued to show promise.