ABSTRACTAn industrial grade protease was immobilized on a prototype, non‐cellulosic tubular ultrafiltration membrane using a purely physical technique based on vacuum adsorption and pH adjustment. A supermarket grade of nonfat dry milk was used to prepare a 0.001 g/ml feed solution which was pumped steadily through the tubular membrane module at 114 L/min. The temperature of the retentate stream in the module was maintained at 50®C and 276 kPag (40 psig) respectively. The prototype system was operated continuously for 240 hr under total recycle conditions and the control (i.e., system without the enzyme) was similarly operated for 50 hr. The degree of flux enhancement of the prototype system relative to the control was impressive. It was estimated that over a period of 240 hr, 93 more permeate was collected for the prototype than for the control. A gradient, lumped parameter mass balance model was formulated for the dynamics of the protein gel layer. The model was simulated on a digital computer, and the various mass transfer and enzyme kinetic parameters were estimated using a Marquardt, nonlinear least squares routine. The resulting curve‐fit was satisfactory, considering the complexities of the process and the simplifying assumptions used in the model develop
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