EXPERIMENTAL DEMONSTRATION OF PH CONTROL FOR A SEQUENTIAL 2-STEP ENZYMATIC-REACTION

pH control for multistep enzymatic synthesis reactions is important di re to its potential industrial applications; however, it becomes diffi cult when the optimal pH for the individual steps of the reaction path way differs by several units. The usual approach of using a compromise d pH is neither satisfactory nor always feasible. An optimal pH contro l technique has been developed which allows a two-step reaction to occ ur simultaneously in proximity to each other and at their respective o ptimal pH in a single reactor. This technique separates the microenvir onments of the two steps of a reaction pathway by coating an immobiliz ed enzyme pellet with a thin layer of urease. Ammonia generated by the hydrolysis of urea consumes the hydrogen ions diffusing from the acid ic bulk solution into the immobilized enzyme pellet. In this paper, th e pH central technique is demonstrated for a two-step reaction where s alicin is first converted by beta-glucosidase to saligenin and glucose , followed by the isomerization of glucose catalyzed by glucose isomer ase. The technique allows this two-step reaction to take place simulta neously at their respective optimal pH values of 5.0 for beta-glucosid ase and 8.0 for glucose isomerase. (C) 1997 Elsevier Science Inc.