Model yeast lysis

The two models of yeast lysis presented here have been developed to serve two different purposes. The simple model is a lumped, two-step model which follows the major features of the data and may prove useful for design of lysis reactors. The structured model, which can account for the source of protein within the cell, was developed to gain a mechanistic basis for predicting the effects of untested process conditions, and to aid insight into the physical processes at work during lysis. 

Figure 3 Simple model simulation of yeast lysis...

The simple and structured model simulations for yeast mass and soluble protein, peptides and carbohydrates are compared in Figure 6 for the yeast and enzyme concentration shown in Figures 3 and 4, and in Figure 7 for a concentrated yeast cell slurry. The simple model fits the data fairly well at both yeast concentrations, in every variable except the peptides. The fit for all variables at longer reaction times is directly related to use of the extent-of-reaction term Y , in the yeast lysis equation. 

Hunter, J.B. and Asenjo, J.A., "Kinetics of enzymatic lysis and disruption of yeast cells 2. A simple model of lysis kinetics" Biotechnol. Bioeng. 1986 (submitted for publication)... 

Structured and Simple Models of Enzymatic Lysis and Disruption of Yeast Cells... 

This paper presents two models of enzymatic lysis of yeast cells a simplified two-step model, accounting for protein release at cell lysis followed by proteolysis, and a more complex mechanistic model which describes the removal of the two layers of the yeast wall and the extrusion and rupture of the protoplast and organelles. 

Parameters for the simple model were determined graphically by Eadie-Hofstee plotting of initial reaction rates and substrate concentrations. Details are given elsewhere (30). As has been observed in hydrolysis of other solid substrates, a residue of non-lysed substrate was found at extended reaction times, when dY/dt tended toward zero. The extent of reaction was strongly dependent on initial substrate and enzyme concentrations (33,34). An empirical funciton for Y was fitted to the ultimate turbidity data for lysis runs at a variety of initial yeast and enzyme concentrations using a least squares method. The calculated values for Yco were used in the simulations (30). Figure 3 shows results of the simple model. 

Hunter JB, Asenjo JA (1987a) Kinetics of enzymatic lysis and disruption of yeast cells 1. Evaluation of two lytic systems with different properties. Biotechnol Bioeng 30 471-480 Hunter JB, Asenjo JA (1987b) Kinetics of enzymatic lysis and disiuption of yeast cells 11. A simple model of lyis kinetics. Biotechnol Bioeng 30 481 90 Hustedt H, Kroner KH, Menge U et al. (1985) Protein recovery using two-phase systems. TIBTECH 3 139-144... 

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