SUGAR-TRANSPORT IN ENZYMATICALLY ACTIVE PROTEINACEOUS MEMBRANES AND THE APPLICATION OF A SORPTION THEORY

The transport of sucrose through lightly crosslinked, reconstituted biopolymeric (i.e., collagen) membranes, blank and enzyme-bound, was investigated. Transient models of the transport mechanism are presented for the following cases: no solute immobilization, and partial solute immobilization, with and without enzymatic reaction. Enzyme-bound collagen membranes were studied through permeation experiments conducted at a system temperature of 25°C so as to examine the effect of reaction on the diffusive transport. The imposed reaction was the enzymatic hydrolysis of sucrose by invertase. An understanding of the sucrose transport mechanism was necessary prior to the analysis of the enzyme membrane permeation data. Through time lag and sorption data collected from blank, unreactive collagen membranes, this mechanism was identified. Upon the elimination of the extramembrane film resistances, a site saturation effect for these membranes was observed. The apparent effective diffusivity was determined from the data collected near system saturation. This value was estimated to be 1.01 × 10-6 cm2/s ± 5%. Thus, a transport pathway on the structural protein is found to control the sugar permeability. The enzyme membrane data reflected a prolonged transient and a significant reduction in the emergent substrate flux. These effects could be important in modeling delays or lags in physiological responses to changes in substrate concentration(s). With the transport mechanism described, the kinetic parameters characterizing these membranes were extractable from these same data. © 1979.