SummaryThe steroid transformation of hydrocortisone to prednisolone, combining the two techniques of immobilized whole cells and high steroid concentrations, was investigated and found to be a feasible process. Freeze-dried Cor.vnebactuiurn simplex cells were immobilized in collagen, tanned with glutaraldehyde, and cast into a membrane. The reaction was studied at hydrocortisone concentrations ranging from 5 to 50 mgiml. The following aspects of the system were examined: I) the substrate concentration effect upon the reaction; 2) the effect of enzyme concentration; 3) the rate-concentration relationship; and 4) the product inhibition characteristics of the system. The optimal substrate concentration was found to be 15 mgiml of a membrane concentration of 80 mgiml. This reaction attained an 80% conversion in 48 hr. A linear relation was found between the initial reaction rate and membrane concentration. One can thus increase the net production of steroid per unit volume and time by increasing the membrane levels. A physical limit to this increase occurred at membrane concentrations greater than 125 mgiml. The rate-concentration relationship was linear when graphed on a Lineweaver-Burk plot; giving a K,' and V,' value of 5.39 mgiml and 0.556 mgimllhr, respectively. When the data were tested for competitive product inhibition, the curves fitted the experimental points fairly well and produced K,' and V,' values of 4.52 mgiml and 0.566 mgimlihr, respectively. Product inhibition experiments showed that the inhibition was not purely competitive. At low substrate concentrations, product inhibited the enzyme; at high substrate concentrations, the enzyme was first stimulated and then depressed by increasing levels of product. This behavior has been analyzed and shown to be possibly a result of the formation of a tertiary intermediate produced during the reaction.
SummaryTwo kinds of mathematical models have been developed for batch penicillin fermentations: (1) general models, b a d on averaged, nondmensionalized cell and penicillin synthesis curves from plant scale fermentom and (2) particular models developed from specific sets of experimental data from two sources. Parameter-temperature functions used with the general models were assumed to have general shapes which could apply to many fermentations, i.e., they were bssed on the familiar temperature response of enzyme-catalyzed reactions. Parameter-temperature functions for the particular models were determined from experimental data for batch runs at various temperatures.
SummaryEnzymatic hydrolysis of insoluble soybean protein by a protease enzyme produced by Penicilliurn duponti K 1104, was investigated in a batch reactor. The reaction conditions were 30-55°C and pH 3.4-3.7. The mechanism of solubilization of the insoluble protein by the Penicilliurn duponri enzyme was deduced from a series of experiments. Kinetic models were developed that involved adsorption followed by peptic digestion of protein, inhibition of low-molecular-weight peptides, and enzyme deactivation. The uncoupled kinetic parameters were estimated using the Marquardt nonlinear parameter estimation algorithm. A bang-bang production of soluble and partially soluble protein is suggested for higher productivity. The essential amino acids pattern of the enzyme-hydrolyzed soy protein was comparable with the unhydrolyzed protein isolate. Aggregation of the soluble protein for an extended time was observable. The low-molecular-weight soluble protein was incorporated into noncarbonated beverages. The amount of protein that could be incorporated into a can of 355 ml noncarbonated beverage, without observable changes in the optical density and also aggregation of the protein, was 2.5 g soluble protein.Beverages with caramel color showed excessive decrease in optical density and precipitation. The kinetics and diffusion in a multipore immobilized-enzyme recycle reactor will be considered in part I1 of this series.
In this study, a cephalosporin C producing strain, Cephalosporium acremonium (ATCC 36225), was chosen to determine the optimal conditions that maximize antibiotic production in a mixed substrate of glucose and sucrose. A model for cell growth and cephalosporin C production at different pH and temperature was developed and the associated parameters were evaluated experimentally. Pontryagin's maximum principle, in conjunction with the model, was used to predict the optimal temperature and pH control profiles to maximize the production of antibiotic.
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