Controlling the pH is essential for enzymatic reactions, as most enzymes only work efficiently within a narrow pH window. This is usually achieved with buffer salts or by titration, which adds cost and complicates the downstream processing. In this work, the authors developed a buffer-free pH control strategy for the enzymatic hydrolysis of urea that relies on the dissolution of gaseous carbon dioxide (CO₂).
CO₂ is itself a by-product of the enzymatic hydrolysis of urea. Instead of removing it, the authors deliberately added it to the reaction in order to regulate the pH and enhance productivity. To analyse and design the process, a kinetic model of urea hydrolysis was coupled with a thermodynamic model of the acid–base equilibria in the aqueous phase, so that the interplay between reaction, CO₂ dissolution and pH could be described consistently.
The resulting concept was successfully demonstrated experimentally, highlighting a practical approach to pH control in enzymatic reactions with minimal downstream processing requirements.
The work was carried out within the CRC 1615 SMART Reactors as a collaboration between the Institute of Technical Biocatalysis and the Institute of Process Systems Engineering at the Hamburg University of Technology. It is associated with the United Nations University Hub on Engineering to Face Climate Change at the Hamburg University of Technology and the United Nations University Institute for Water, Environment and Health (UNU-INWEH).
Kayla Dittmer, Chloe Ng-Brossard, Leandros Paschalidis, Daniel Ohde, Mirko Skiborowski, Andreas Liese (2026). CO₂-Driven pH Control in the Enzymatic Hydrolysis of Urea: A Coupled Modeling-Experiment Approach.
