Showing papers by "Paul F. Greenfield published in 1981"
TL;DR: Values of the deactivation rate constant obtained by regression analysis were independent of particle type and size and reactor description indicating that they were in fact inherent characteristics of the immobilized enzymes which are immobilized on supports and which undergo substrate or parallel poisoning.
Abstract: An approximate analytical solution which describes the deactivation of catalase immobilized on porous supports is provided. Catalase was chosen as an example of an enzyme which undergoes parallel poisoning. The solution incorporates the effects of pore diffusion and of the parallel poisoning. The solution incorporates the effects of pore diffusion and of the parallel poisoning of catalase by its substrate hydrogen peroxide into a time dependent effectiveness factor which can then be inserted into the appropriate reactor equations. The model was tested by measuring experimentally the deactivation of immobilized catalase in both a packed bed reactor and a continuous stirred basket reactor and was found to be very satisfactory at inlet substrate concentrations of less than 0.02M. Values of the deactivation rate constant obtained by regression analysis were independent of particle type and size and reactor description indicating that they were in fact inherent characteristics of the immobilized enzymes which are immobilized on supports and which undergo substrate or parallel poisoning.
20 citations
TL;DR: In this paper, an approximate analytical technique employing a finite integral transform was developed to solve the reaction diffusion problem with Michaelis-Menten kinetics in a solid of general shape, and a simple infinite series solution for the substrate concentration was obtained as a function of the Thiele modulus, modified Sherwood number, and Michaelis constant.
Abstract: An approximate analytical technique employing a finite integral transform is developed to solve the reaction diffusion problem with Michaelis-Menten kinetics in a solid of general shape. A simple infinite series solution for the substrate concentration is obtained as a function of the Thiele modulus, modified Sherwood number, and Michaelis constant. An iteration scheme is developed to bring the approximate solution closer to the exact solution. Comparison with the known exact solutions for slab geometry (quadrature) and numerically exact solutions for spherical geometry (orthogonal collocation) shows excellent agreement for all values of the Thiele modulus and Michaelis constant.
11 citations
TL;DR: In this paper, the concept of improving ethanol productivity in batch fermentation by utilizing two organisms with different substrate and product inhibition characteristics was examined, and the inocula consisted of two yeasts chosen because of their different inhibition properties at high sugar and high ethanol concentrations respectively.
Abstract: The concept of improving ethanol productivity in batch fermentation by utilising two organisms with different substrate and product inhibition characteristics was examined. The inocula consisted of two yeasts chosen because of their different inhibition properties at high sugar and high ethanol concentrations respectively. Improved productivity was found in the dual system. A numerical analysis which incorporates the non-linear nature of the inhibition demonstrates the level of improvement which might be attained in such systems.
10 citations