Understanding the influence of temperature change and cosolvent addition on conversion rate of enzymatic suspension reactions based on regime analysis

It is a commonly held belief that enzymatic conversions of substrate in aqueous suspensions can be speeded up by raising the temperature or adding organic solvents to promote dissolution of the substrate. To quantify the impact of such changes, we studied the α‐chymotrypsin‐catalyzed hydrolysis of dimethyl benzylmethylmalonate as a model system. It was found that, upon addition of organic cosolvents, longer process times were actually required, even though the substrate solubility increased severalfold as expected. Upon raising the temperature from 25°C to 37°C, on the other hand, both the substrate solubility, the substrate dissolution rate, and the enzymatic reaction rate increased, leading to shorter process times. A dissolution–reaction model incorporating the kinetics of enzyme deactivation could be developed. A simple relation for the prediction of the overall process time was established by evaluating the time constants for the subprocesses: substrate dissolution; enzymatic conversion; and enzyme deactivation. Using regime analysis, rules of thumb for the optimization of an enzymatic suspension reaction were derived. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 125–134, 1999.