Demonstration of pH control in a commercial immobilized glucose isomerase

✍ Scribed by Ronald L. Fournier; Sasidhar Varanasi; James P. Byers; Guodong Chen

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 517 KB
• Volume: 52
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/(sici)1097-0290(19961220)52:6<718::aid-bit10>3.0.co;2-7

✦ Synopsis

The synthesis of a variety of important biochemicals involves multistep enzyme-catalyzed reactions. In many cases, the optimal operating pH is much different for the individual enzymatic steps of such synthesis reactions. Yet, it may be beneficial if such reaction steps are combined or paired, allowing them t o occur simultaneously, in proximity to one another, and at their respective optimal pH. This can be achieved by separating the microenvironments of the two steps of a reaction pathway using a thin urease layer that catalyzes an ammoniaforming reaction. In this article, the pH control system in a commercial immobilized glucose (xylose) isomerase pellet, which has an optimal pH of 7.5, is demonstrated. This system allows the glucose isomerase to have near its optimal pH activity when immersed in a bulk solution of pH 4.6. A theoretical analysis is also given for the effective fraction of the immobilized glucose isomerase, which remains active when the bulk pH is at 4.6 in the presence of 20 mM urea versus when the bulk pH is at its optimal pH of 7.5. Both theoretical and experimental results show that this pH control system works well in this case.