Gd. Chen et al., EXPERIMENTAL DEMONSTRATION OF PH CONTROL FOR A SEQUENTIAL 2-STEP ENZYMATIC-REACTION, Enzyme and microbial technology, 21(7), 1997, pp. 491-495
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.