The Chemical Engineering Journal最新文献

The enzymatic hydrolysis of potato pulp by a cell-free culture filtrate of Trichoderma reesei Rut C30 was studied. On the basis of the experimental data a dynamic unstructured model using Michaelis—Menten kinetics was developed. This mathematical model describes the enzymatic hydrolysis in terms of the adsorption and desorption of enzymes on the solid substrate and with regard to competitive and uncompetitive inhibition. The model equations consist of a non-linear system of ordinary differential and algebraic equations. Parameter identification was done by dividing the model into submodels and fitting these to experimental data.

The simulation results with the model correspond well with the experimental data. Thus the good agreement between simulated and measured process variables indicates that the model is suitable for description of the enzymatic hydrolysis. Computations for different operational conditions show the range of validity and performance of the model. Possibilities for improvements in yield and productivity could be deduced by model computations.

On the basis of the similarity of the shapes of the liquid heat capacity and vapour pressure curves, and the concept that a property such as heat capacity (energy storage capacity) should directly depend on the constitution and structure of the molecules, a corresponding state-type relation has been formulated and tested: C_σL = R_M(5.4571 − $\text{0.3098}\text{T}{}_{\mathrm{R}}\text{− 1}$) where C_σL (J mol⁻¹ K⁻¹) is the saturated liquid heat capacity, R_M (cm³ mol⁻¹) is the molar refraction and T_R is the reduced temperature. The extension of the method, which predicts liquid heat capacities of pure non-polar liquids with an average absolute deviation of 5.5%, to polar liquids and several binary mixtures is also discussed.

The kinetics of growth, substrate consumption and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) production by Escherichia coli C600 galK (GAPDH) have been studied. Using the corresponding observations, an unstructured physiological model has allowed description of the behaviour of the recombinant strain in batch culture on a selective complex medium. This model is characterized by two physiological states (glucose and acetic acid consumption) and is based on the Monod equation applied to the growth rate combined with inhibition by acetate. Since the strain used is genetically engineered, it also incorporates the probability of plasmid loss which has been modelled previously. The model has been applied to a set of batch cultures at varying initial glucose concentrations. According to the simulation results, the model provides an excellent fit to the experimental results.

Inactivation of micro-organisms with pressurized carbon dioxide at both supercritical and subcritical temperatures has been studied recently. This method differs conceptually from other processes in that the action of cell inactivation is prompted primarily by the extraction of intracellular substances from cells or cell membranes. Disturbance or damage to the balance of the biological system of the cell can cause death without rupture of the cell wall. Experimental results showed that Leuconostoc dextranicum cells were inactivated at least 10⁸-fold at 35 °C in 15 and 20 min under CO₂ pressures of 1000 and 3000 lbf in⁻² respectively. Subcritical carbon dioxide is less effective, requiring about 40 and 35 min at these pressures to inactivate the same amount of cells. The inactivation rate is controlled essentially by the penetration of CO₂ into the microbial cells, which at a sufficient level extracts lipids or other vital constituents to achieve the lethal effect. Various important parameters of the inactivation process are explored.

The solubilities of carbon dioxide in 18 normal paraffin solvents are modelled by the Soave equation of state with one interaction parameter. Henry's constant, the partial molar volume at infinite dilution and the Margules constant are evaluated from the above parameters using Bender et al.'s (Fluid Phase Equilib., 15 (1984) 241) approach and these properties are shown to be dependent on temperature and the carbon number of normal paraffins.

The use of enzymes in waste treatment processes has been proposed by a number of investigators. However, most of this work has focused on demonstrating the disappearance of target pollutants and has not considered the engineering issues that will ultimately determine the process feasibility. The conditions that occur in most waste treatment situations are very different from the conditions that exist in chemical manufacturing processes, so the technical concerns in implementing enzyme technology cannot be extrapolated directly from experience in the manufacturing sector. The waste treatment situations that may be appropriate for enzyme technology are presented, along with criteria for enzymes that may be of near-term applicability. Previous work on the waste treatment applications of enzymes is reviewed and the technical issues that must be considered in feasibility determinations are discussed.

The purpose of this investigation was to select the lowest energy-consuming configuration of a ribbon agitator. The criterion of the selection was mixing energy. The interaction between power consumption, mixing time and the geometric parameters of a non-typical helical ribbon agitator was also investigated.

Three activated carbons from olive stones have been used in this study. Their surface area ranges from 1127 to 1350 m² g⁻¹ and their pore volume accessible to water from 0.491 to 0.682 cm³ g⁻¹. The behaviour of these activated carbons to remove tannic acid from aqueous solutions, under both static and dynamic conditions, has been studied. Under static conditions their adsorption capacity varies from 54.2 to 96.2 mg g⁻¹; whereas under dynamic conditions only a low fraction of this capacity is utilized (less than 2%). All these results are discussed on the basis of the textural characteristics of the activated carbons.