The influence of temp. on the catalytic activity and deactivation of sol. enzymes which are com. used in batch processes is discussed. Since high temp. not only accelerates the desired enzymic reaction but also the undesired deactivation of the enzyme, it is important to obtain a temp. which balances both processes. A math. model is presented which describes the temp. at which the amt. of enzyme required to accomplish the desired reaction is minimal. The hydrolysis of lactose to glucose and galactose by lactase of Aspergillus oryzae is used as an example. Reversible and irreversible deactivation of lactase is discussed, and the amt. of enzyme required for the reaction given as a function of temp. Since sol. enzymes cannot be recovered in discontinuous processes, it is very cost effective to utilize such math. models to det. the optimum temp. which is needed to complete the enzymic process efficiently. [on SciFinder (R)]