SIMPLE DISSOLUTION-REACTION MODEL FOR ENZYMATIC CONVERSION OF SUSPENSION OF SOLID SUBSTRATE

Although reactions in substrate suspension are employed in industry fo r several bioconversion processes, there appears to be no quantitative model available in the literature to rationalize the optimization of these processes. We present a simple model that incorporates the kinet ics of substrate dissolution and a simultaneous enzymatic reaction. Th e model was tested in the alpha-chymotrypsin-catalyzed hydrolysis of a n aqueous suspension of dimethyl benzylmethylmalonate to a homogeneous solution of enantiomerically pure monoester. This reaction occurs in the bulk phase, so catalysis by enzyme absorbed at the solid-liquid in terface plays no role. The value of the parameters in the model (i.e., the mass transfer coefficient of substrate dissolution (k(L)), the su bstrate solubility, and the rate constant for the enzymatic reaction) were determined in separate experiments. Using these parameter values, the model gave a good quantitative prediction of the rate of the over all dissolution-reaction process. When the particle size distribution is known, k(L) may also be calculated instead. The model seems to be a pplicable also for other poorly soluble substrates, other enzymes, and other solvents. (C) 1997 John Wiley & Sons, Inc.