bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen transfer and mixing in a tower cycling fermentor
Authors: Lin C. H. , Fang B. S. , Wu C. S. , Fang H. Y. , Kuo T. F. , Hu C. Y.
Published: December 2004

Tower cycling fermentors for the production of single‐cell protein from volatile substrates were studied. The mass transfer, mixing and circulation patterns, and residence time distribution (RTD) curves were investigated in these vessels. This study suggests that the tower cycling fermentors for volatile substrates fermentation may improve product yields and at the same time reduce the power consumption, thereby resulting in a significant increase in operating cost savings and capital profits. The results of this research further indicate a future potential for commercial scale tower cycling fermentors.
Immobilization of enzymes based on hydrophobic interaction. I. Preparation and properties of a β‐amylase adsorbate
Authors: Caldwell Karin Dahlgren , Axén Rolf , Wall Margareta Berg , Porath Jerker
Published: December 2004

Sweet potato β‐amylase (α‐1,4 glucan maltohydrolase, EC 3.2.1.2) was immobilized through adsorption onto an agarose gel to which nonpolar side chains had been introduced via ether bridges.

The adsorbent showed evidence of saturation at an enzyme content of 35 mg per milliliter of packed gel. The adsorption was rapid and yielded a product whose operational stability depended on the initial content of β‐amylase. Activity leakage was low. The relative activity of immobilized enzyme was inversely related to the amount of enzyme adsorbed to a given gel volume, having a maximal value of around 50% at low enzyme contents.
Bacterial yields on methanol, methylamine, formaldehyde, and formate
Authors: Goldberg I. , Rock J. S. , Ben‐Bassat A. , Mateles R. I.
Published: December 2004

Several bacteria utilizing C1‐compounds as sole carbon sources were grown on these substrates in continuous culture. The molar yield values (g of cell dry wt/mol of substrate utilized) of bacteria which utilize C1‐compounds via the ribulose monophosphate pathway were between 15.7 to 17.3 when grown on methanol; while the molar yield values of bacteria which use the serine pathway for the assimilation of C1‐compounds varied between 9.8 and 13.1. The molar yield values of different bacteria which use the serine pathway decreased as the oxidation levels of the C1‐growth substrates increased. On formaldehyde the values were between 7.2 to 9.6, whereas on formate the values varied from 3.3 to 6.9.

It appears that bacteria utilize Cl‐compounds more efficiently via the ribulose monophosphate pathway than via the serine pathway. The oxidation step from methanol to formaldehyde (and from methylamine to formaldehyde) in the bacteria studied may be energy yielding. A comparison has been made between the experimental yield values obtained and theoretical values.
Galactose Oxidase: Applications of the covalently immobilized enzyme in a packed Bed configuration
Authors: Dahodwala S. K. , Weibel M. K. , Humphrey A. E.
Published: December 2004

Galactose oxidase (E.G. 1.1.3.9) was covalently immobilized to chemically modified porous silica particles by reaction of the native enzyme with pendant benzoyl azide groups on the carrier. The enzyme loading on the carrier was 100–150 units per milliliter. The immobilized enzyme was incorporated into a hardware assembly suitable for the determination of galactose or lactose concentrations in complex biological fluids. The prototype instrument as described is suitable for continuous, on‐line monitoring or discrete sample analysis. Reaction conditions can be readily provided which maintain global first order kinetics within the reactor and strict linearity of the procedure over a wide range of sample concentrations. Auto‐inactivation of the immobilized enzyme can be prevented by K3Fe(CN)6 and long‐term reactor stability can be achieved by the periodic application of the reagent to the enzyme reactor in situ.
The application of constant recycle solids concentration in completely mixed oxygen activated sludge process
Authors: Lin L. J. , Yang P. Y.
Published: December 2004

For better operational control of the completely mixed oxygen activated sludge process (CMOAS), a study concerning the kinetics, performance, and operational stability of the Ramanathan‐Gaudy model was conducted. Short‐term experiments were conducted at various dilution rates (1/9, 1/6, 1/3, 1/1.5, and 1/1.0 hr−1) by using two recycle solids concentration values (5000 and 10,000 mg/liter). The influent substrate was an actual industrial organic wastewater (soft drink waste) and its concentration was maintained at 1000 mg/liter COD. The hydraulic recycle ratio, α, was maintained at 0.30.

It was found that for CMOAS system with constant recycle cell concentration, a “steady state” with respect to reactor biological solids and effluent COD at different dilution rates could be attained. No appreciable dilute‐out of reactor biological solids and substrate was observed up to the dilution rate of 1 hr−1 for both systems of different XR (5000 and 10,000 mg/liter). For the system of XR = 5000 mg/liter, except the dilution rate of hr−1, the effluent filtrate COD was lower than 100 mg/liter, the aerator biological solids concentration was about 1550 mg/liter, and the COD removal efficiency was higher than 90% for all dilution rates. For the system of XR = 10,000 mg/liter, the effluent filtrate COD was lower than 71 mg/liter, the aerator biological solids concentration was about 2750 mg/liter, and the COD removal efficiency was higher than 90% throughout all the dilution rates selection in the present study. The value of the Sludge Volume Index (SVI) was the range of 37.0 to 58.5 and provided good settleability of sludge. The sludge yield was 0.53 for the system of XR = 5000 mg/liter and 0.57 for the system of XR = 10,000 mg/liter. The carbohydrate and the protein content of the cells were 10.1–21.6% and 35.6–50.6%, respectively.

For predicting the reactor biological solid and effluent COD of the CMOAS system by using the Ramanathan‐Gaudy model, two sets of values for the biological kinetic constants should be considered since it provided the best fit of predicted values of the observed values. In the present study, μm = 0.4 hr−1, ks = 92 mg/liter for 1/3 ⩽ D ⩽ 1, and μm = 0.05 hr−1, ks = 11.1 mg/liter for 1/9 ⩽ D < 1/3 were used to calculate the predicted values of reactor biological solid and effluent filtrate COD.
Continuous proteolysis with a stabilized protease. I. Chemical stabilization of an alkaline protease
Authors: Boudrant J. , Cuq J. L. , Cheftel C.
Published: December 2004

Due to the loss of enzymatic activity as a function of time, an alkaline protease, selected for the continuous preparation of protein hydrolysates (J. Boudrant and C. Cheftel, Biotechnol. Bioeng., 18, 1735, 1976), was chemically stabilized by a simple treatment with glutaraldehyde. Two fractions, soluble and insoluble, were obtained. The activities of these two fractions were measured with casein and N‐benzoyl‐L‐arginine ethyl ester (BAEE) as a function of glutaraldehyde concentration used. It was noted that the insoluble fraction was practically inactive with the first substrate and that the heat stability of the soluble form was likewise enhanced. Molecular weights of these two forms were unchanged, but the uv‐spectrum of the soluble form was modified. From amino acid analysis, it appears that this treatment mainly provokes a decrease in lysine content.
Continuous proteolysis with a stabilized protease. II. Continuous experiments
Authors: Boudrant J. , Cheftel C.
Published: December 2004

Batch proteolysis experiments were performed in order to choose a protein–protease system to prepare a correct hydrolysate suitable for the enrichment of soft‐drinks. The system eventually studied was casein–Alcalase.

Comparative batch and continuous proteolysis of casein by Alcalase showed that the reaction, which does not exactly follow first order kinetics with respect to the substrate concentration, is inhibited by the reaction products. Furthermore, experiments were done in order to determine the reaction conditions (pH 8.8 in the reactor, casein concentration 5%, 40°C). Determining the molecular weight of Alcalase (43,000) suggested the choice of ultrafiltration membrane PM 30.

Studies of continuous proteolysis with the chemically stabilized enzyme retained by the ultrafiltration reactor showed that protease reuse for seven days at 40°C is possible and that the growth of microorganisms is practically inhibited under these conditions. Gel chromatography showed the molecular weight range of the peptides to be less than 2,000. Triangular taste tests showed that the threshold identification concentration of the dry hydrolysate in orange juice is about 0.65%.
Modelling Xanthomonas campestris batch fermentations in a bubble column
Authors: Pons A. , Dussap C. G. , Gros J. B.
Published: December 2004

Rate and yield expressions relating to biomass and xanthan formation and to nitrogen, glucose, and oxygen consumption were established for Xanthomonas campestris batch fermentations in a bubble column. Microbial growth was described by the logistic rate equation, characterized by a maximum specific growth rate μM = 0.5 h−1 and a maximum attainable cell concentration provided by nitrogenous compounds. With regard to carbon metabolism, the decrease with time in experimental yields and in the experimental specific rates of xanthan production and glucose assimilation demonstrated the inadequacy of the Luedeking–Piret model. These decreases were connected to the simultaneous drop in dissolved‐oxygen tension observed during xanthan synthesis. The knowledge of metabolic pathways and energetic balance were used to establish the relationships between substrate utilization, ATP generation, and xanthan production. The model was structured by assuming the oxygen limitation of both the respiration rate and the efficiency of the oxidative phosphorylation mechanism (P/O ratio). Consequently, the specific rates and yield expressions became dependent on the dissolved‐oxygen tension, i.e., of the volumetric oxygen transfer in the fermentor.
Transient method for proposing the mechanisms of reactions over immobilized enzymes
Authors: Wu Jau‐Yann , Weng Hung‐Shan
Published: December 2004

The transient response method is introduced to elucidate the mechanism of reaction over immobilized enzyme. Glucose oxidation over the glucose oxidase that was immobilized on ion‐exchange resin using glutaraldehyde as a linking agent is selected as an example here. The transient responses of a fixed‐bed reactor to step increases and decreases in glucose, oxygen, and gluconolactone feed concentrations have been monitored and interpreted. From some responses, we have found that gluconolactone is formed in the reaction of glucose with adsorbed oxygen, while hydrogen peroxide is formed in the reaction of oxygen with adsorbed glucose. Combining all information from interpreting the responses with the literature, a mechanistic picture can be obtained as follows:

.
An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the presence of Thiobacillus ferrooxidans
Authors: Pesic B. , Oliver D. J. , Wichlacz P.
Published: December 2004

The oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+ < 0.001M, T < 25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression:

Below pH = 2.2, the oxidation rate is independent of H+ Concentration.
Impossibility of coexistence of three pure and simple competitors in configurations of three interconnected chemostats
Authors: Chang Shiuan‐Wu , Baltzis B. C.
Published: December 2004

It is well established that pure and simple microbial competitors cannot coexist at a steady state if their environment is homogeneous. For the case of two microbial populations competing purely and simply in two interconnected chemostats having time‐invariant input(s), it is known from the literature that a stable steady state of coexistence arises in domains of the operating parameters space and is attributed to the spatial heterogeneities of the system, which allow a different species to have the competitive advantage in each one of the two sub‐environments. This article investigates whether the aforementioned result can be extended to the case of three species competing in three interconnected vessels. By studying all possible alternate configurations of the three‐chemostat system, it is shown that coexistence of the three species is impossible, except possibly for some discrete values of the operating parameters. Some potential explanations for the results are discussed.
Transient responses of hybridoma cells to nutrient additions in continuous culture: I. Glucose pulse and step changes
Authors: Miller William M. , Wilke Charles R. , Blanch Harvey W.
Published: December 2004

Glucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady‐state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100–200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by‐product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day−1. The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.
Different modes of hydrocarbon uptake by two Pseudomonas species
Authors: Goswami Pranab , Singh H. Devendra
Published: December 2004

The mode of n‐hexadecane uptake by two organisms—Pseudomonas M 1 and Pseudomonas N 1—was studied. During the growth of Pseudomonas M 1 on n‐hexadecane, no extracellular biosurfactant/bioemulsifier was produced, no significant n‐hexadecane pseudosolubilization was observed, and the reduction of surface and interfacial tensions in the cell‐free culture broth was negligible. EDTA, a known inhibitor of hydrocarbon pseudosolubilization, did not inhibit the growth of the organism on n‐hexadecane. Normal hexadecane‐grown cells showed strong surface‐active properties and capacity to adhere firmly to hydrocarbon phase. It was concluded that in this organism, surface‐active properties of the cells facilitate attachment of cells to the hydrocarbon–water interface generated by agitation, and promote substrate uptake and growth; no hydrocarbon pseudosolubilization or extracellular mediator is involved in the substrate uptake. Pseudomonas N 1 grew on n‐hexadecane much faster than Pseudomonas M 1. Growth of this organism on n‐hexadecane was associated with the extracellular production of biosurfactant–bioemulsifier and n‐hexadecane pseudosolubilizing factor; the growth was strongly inhibited by 5 mM EDTA, indicating that hydrocarbon pseudosolubilization was the dominant factor in substrate uptake. The rate of n‐hexadecane pseudosolubilization was high enough to account for the substrate up take rate. Hydrocarbon emulsifying and n‐hexadecane pseudosolubilizing factors were isolated and tentatively characterized as lipoprotein and glycoprotein, respectively. Both factors act in a synergistic manner to provide enhanced hydrocarbon transport to cells through pseudosolubilization. It is proposed that this facility of mediated hydrocarbon transport is the basis for the relatively fast rate of growth of Pseudomonas N 1 on hydrocarbon.
Cellulase production by Trichoderma reesei when cultured on xylose‐based media supplemented with sorbose
Authors: Schaffner D. W. , Toledo R. T.
Published: December 2004

The ability of L‐sorbose to stimulate cellulase production In shake flask culture of Trichoderma reesei was examined in mineral salts media (initial pH 5.0) containing either 1.0% D‐xylose, 1.0% cellulose, and/or 0.1, 0.3, or 0.5% L‐sorbose. When sorbose was the only carbon source, growth was limited, little substrate was utilized, pH increased, and cellulase activity was not apparent. The other carbon sources promoted good growth, pH dropped sharply to 2.5–3.0, substrate was utilized rapidly, and cellulase activity was detected. After three weeks of fermentation, twice as much cellulase activity was detected in the medium containing only cellulose as the carbon source, as compared to xylose as the carbon source. Cellulase activity was higher when media contained xylose supplemented with sorbose compared to xylose as the only carbon source. At 0.3 and 0.5% levels of sorbose supplementation of xylose‐based media, cellulase activity was similar to that in cellulose‐based media.
An alternate method for estimation of cell growth kinetics from batch cultures
Authors: Lee Jeewon , Chang Hsiao‐Lung , Parulekar Satish J. , Hong Juan
Published: December 2004

An alternative to estimation of cell growth kinetics via continuous culture experiments is proposed in this article. The method employed is based on batch culture experiments with very small inocula (initial cell concentrations being typically less than 5000 cells/mL). Such low initial cell concentrations result in extended exponential cell growth phase during which culture conditions remain unchanged, thereby permitting precise estimation of specific cell growth rates from batch experiments especially for fast‐growing microorganisms such as Bacillus species. The effectiveness and utility of this approach are demonstrated via several experiments conducted with a wild‐type strain (Bacillus subtilis TN106) and a recombinant strain (B. subtilis TN106[pAT5]). True establishment of exponential growth phase requires insignificant variance of most of the culture conditions during the initial growth phase. Satisfaction of this requirement is demonstrated for microbial systems investigated here. This approach is especially well suited for recombinant microorganisms containing segregationally unstable plasmids, since estimation of growth kinetics of these from continuous cultures is very difficult and highly unreliable due to continual reversion of recombinant ceils to plasmid‐free host cells unless some selection pressure is applied at levels sufficient to keep the presence of plasmid‐free cells minimal.
Kinetic study of hybridoma cell growth in continuous culture. I. A model for non‐producing cells
Authors: Frame Kelly K. , Hu Wei‐Shou
Published: December 2004

The kinetic behavior of a nonproducing hybridoma clone AFP‐27‐NP was investigated in continuous culture under glucose‐limited conditions. A total of more than 21, 000 h of cultures were operated at dilution rates ranging from 0.01 to 0.06 h−1. The viable cell concentrations, dead cell concentrations, and cell volumes all varied with the dilution rate. A steady‐state model was developed based on the biomass concentration and the glucose concentration. The specific growth rate as a function of glucose concentration is described by a model similar to the Monod model with a threshold glucose concentration and a minimum specific growth rate incorporated; the model is meaningful only at glucose concentrations and specific growth rates above these levels. A death rate is included in the model which is described by an inverted Monod‐type function of glucose concentration. The yield coefficient based on glucose is constant in the lower range of specific growth rates and changes to a new constant value in the upper region of specific growth rates. No maintenance term for glucose consumption was needed; in the plot of specific glucose consumption rate vs. specific growth rate, the line intercepted the specific growth rate axis at a value close to the minimum growth rate. The values for the model parameters were determined from regression analysis of the steady‐state data. The model predictions and experimental results fit very well.
Some considerations for optimization of desorption chromatography
Authors: Gu Tingyue , Tsai Gow‐Jen , Tsao George T.
Published: December 2004

The effect of isotherm parameters of a displacer on the efficiency of desorption Chromatography has been investigated numerically. A general nonlinear multicomponent rate equation model with Langmuir isotherm was used in this study. It was found that the best displacer in this kind of operation is usually not the one that is more strongly adsorbed than the adsorbates when the operation is to displace and concentrate the adsorbates from a saturated or partially saturated column and to minimize the amount of displacer used. The desorption Chromatography is different from the classical displacement development in both operational purpose and the requirement for the displacer. The desorption Chromatography in industrial practice was also analyzed and discussed for the case in which the displacer is introduced in either the same or the reverse flow direction after an incomplete frontal adsorption operation.
Model of oxygen transport limitations in hollow fiber bioreactors
Authors: Piret James M. , Cooney Charles L.
Published: December 2004

Axial and radial oxygen depletion are believed to be critical scale‐limiting factors in the design of cell culture hollow fiber bioreactors. A mathematical analysis of oxygen depletion has been performed in order to develop effectiveness factor plots to aid in the scaling of hollow fiber bioreactors with cells immobilized in the shell‐side. Considerations of the lumen mass transport resistances and the axial gradients were added to previous analyses of this immobilization geometry. An order of magnitude analysis was used to evaluate the impact of the shell‐side convective fluxes on the oxygen transport. A modified Thiele modulus and a lumen and membrane resistance factor have been derived from the model. Use of these terms in the effectiveness factor plots results in a considerable simplification of the presentation and use of the model. Design criteria such as fiber dimensions and spacing, reactor lengths, and recycle flow rates can be selected using these plots. Model predictions of the oxygen limitations were compared to experimental measurements of the axial cell distributions in a severely oxygen limited hollow fiber bioreactor. Despite considerable uncertainty in our parameters and nonidealities in hollow fiber geometry, the cell distribution correlated well with the modeling results.
Simultaneous saccharification and fermentation of cellulose to lactic acid
Authors: Abe Shin‐ichiro , Takagi Motoyoshi
Published: December 2004

Recent interest in the industrial manufacture of ethanol and other organic chemicals from biomass has led to the utilization of surplus grain and cane juice as a fermentation feedstock. Since those starting materials are also foods, they are expensive. As an alternative, cellulosic substances—the most abundant renewable resources on earth1—have long been considered for conversion to readily utilizable hydrolyzates.2, 3

For the production of ethanol from cellulose, we have proposed the simultaneous saccharification and fermentation (SSF) process.4 In SSF, enzymatic cellulose hydrolysis and glucose fermentation to ethanol by yeast proceed simultaneously within one vessel. The process advantages—reduced reactor volume and faster saccharification rates—have been confirmed by many researchers.5–8 During SSF, the faster saccharification rates result because the glucose product is immediately removed, considerably diminishing its inhibitory effect on the cellulase system.9

To effectively apply the SSF method to produce substances fermented from glucose, several conditions should be satisfied. One is coincident enzymatic hydrolysis and fermentation conditions, such as pH and temperature. The other is that cellulase inhibition by the final product is less than that by glucose and/or cellobiose. One of us has reported that acetic acid, citric acid, itaconic acid, α‐ketoglutaric acid, lactic acid, and succinic acid scarcely inhibit cellulase.10 This suggests that if the microorganisms which produce these organic acids were compatible with cellulase reaction conditions, the organic acids could be produced efficiently from cellulosic substrates by SSF.

In this article, the successful application of SSF to lactic acid production from cellulose is reported. Though there have been several reports of direct cellulose conversion to organic acids by anaerobes such as Clostridium, only trace amounts of lactic acid were detected in the fermentation medium among the low‐molecular‐weight fatty acid components.11–13 Lactic acid is one of the most important organic acids and has a wide range of food‐related and industrial applications.
Use of fluorometry for monitoring and control of a bioreactor
Authors: Li Jain‐Ke , Humphrey Arthur E.
Published: December 2004

A new fluorescent bioreactor monitoring probe—multiple excitation fluorometric system (MEFS)—has been developed. This probe was compared to the commercially available BioChem Technology FluroMeasure system (NADH probe). In this task the fluorescence behavior of three model fermentation systems, ethanol fermentation by Candida utilis, phenol fermentation by Pseudomonas putida, and glucose fermentation by Saccharomyces cerevisiae, were examined. The results indicated that the fluorescence intensity and behavior of various cellular fluorophors vary significantly between the different fermentation systems. Monitoring a fermentation process using only NAD(P)H fluorescence provided limited information. The NAD(P)H fluorescence was found not to be the best fluorescence signal for monitoring cell concentrations. The best way of monitoring a bioreactor by fluorometry may be to monitor several fluorophors in the whole culture broth simultaneously and to relate these fluorescence signals to various biological parameters.
Optimization of batch processes involving simultaneous enzymatic and microbial reactions
Authors: Asenjo J. A. , Sun W.‐H. , Spencer J. L.
Published: December 2004

Two general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
Extractive fermentation for lactic acid production
Authors: Yabannavar V. M. , Wang D. I. C.
Published: December 2004

Lactic acid extractive fermentation was demonstrated using Alamine 336 in oleyl alcohol at acidic pH. The use of an efficient extraction system was possible through employment of the cell immobilization procedure. Process modeling was performed to relate the various process parameters such as flow rate, concentration, and pH. In experiments with 15% Alamine 336/oleyl alcohol, the bioreactor operation resulted in a higher productivity (12 g/L gel h) compared to that of a control fermentation (7 g/L gel h). Strategies for optimizing the extractive fermentation process were proposed considering both productivity and product recovery.
Optimization of L‐malic acid production by Aspergillus flavus in a stirred fermentor
Authors: Battat Emil , Peleg Yoav , Bercovitz Amir , Rokem J. Stefan , Goldberg Israel
Published: December 2004

Effects of various nutritional and environmental factors on the accumulation of organic acids (mainly L‐malic acid) by the filamentous fungus Aspergillus flavus were studied in a 16‐L stirred fermentor. Improvement of the molar yield (moles acid produced per moles glucose consumed) of L‐malic acid was obtained mainly by increasing the agitation rate (to 350 rpm) and the Fez+ ion concentration (to 12 mg/L) and by lowering the nitrogen (to 271 mg/L) and phosphate concentrations (to 1.5 mM) in the medium. These changes resulted in molar yields for L‐malic acid and total C4 acids (L‐malic, succinic, and fumaric acids) of 128 and 155%, respectively. The high molar yields obtained (above 100%) are additional evidence for the operation of part of the reductive branch of the tricarboxylic acid cycle in L‐malic acid accumulation by A. flavus. The fermentation conditions developed using the above mentioned factors and 9% CaCO3 in the medium resulted in a high concentration (113 g/L L‐malic acid from 120 g/L glucose utilized) and a high overall productivity (0.59 g/L h) of L‐malic acid. These changes in acid accumulation coincide with increases in the activities of NAD+‐malate dehydrogenase, fumarase, and citrate synthase.
Combination of support vector machines (SVM) and near‐infrared (NIR) imaging spectroscopy for the detection of meat and bone meal (MBM) in compound feeds
Authors: Pierna J. A. Fernández , Baeten V. , Renier A. Michotte , Cogdill R. P. , Dardenne P.
Published: December 2004

This study concerns the development of a new system to detect meat and bone meal (MBM) in compound feeds, which will be used to enforce legislation concerning feedstuffs enacted after the European mad cow crisis. Focal plane array near‐infrared (NIR) imaging spectroscopy, which collects thousands of spatially resolved spectra in a massively parallel fashion, has been suggested as a more efficient alternative to the current methods, which are tedious and require significant expert human analysis. Chemometric classification strategies have been applied to automate the method and reduce the need for constant expert analysis of the data. In this work the performance of a new method for multivariate classification, support vector machines (SVM), was compared with that of two classical chemometric methods, partial least squares (PLS) and artificial neural networks (ANN), in classifying feed particles as either MBM or vegetal using the spectra from NIR images. While all three methods were able to effectively model the data, SVM was found to perform substantially better than PLS and ANN, exhibiting a much lower rate of false positive detection. Copyright © 2004 John Wiley & Sons, Ltd.
Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M2[C2O4] (M=K, Rb, Cs)
Authors: Dinnebier Robert E. , Vensky Sascha , Jansen Martin , Hanson Jonathan C.
Published: December 2004

The high‐temperature phases of the alkali‐metal oxalates M2[C2O4] (M=K, Rb, Cs), and their decomposition products M2[CO3] (M=K, Rb, Cs), were investigated by fast, angle‐dispersive X‐ray powder diffraction with an image‐plate detector, and also by simultaneous differential thermal analysis (DTA)/thermogravimetric analysis (TGA)/mass spectrometry (MS) and differential scanning calorimetry (DSC) techniques. The following phases, in order of decreasing temperature, were observed and crystallographically characterized (an asterisk denotes a previously unknown modification): *α‐K2[C2O4], *α‐Rb2[C2O4], *α‐Cs2[C2O4], α‐K2[CO3], *α‐Rb2[CO3], and *α‐Cs2[CO3] in space group P63/mmc; *β‐Rb2[C2O4], *β‐Cs2[C2O4], *β‐Rb2[CO3], and *β‐Cs2[CO3] in Pnma; γ‐Rb2[C2O4], γ‐Cs[C2O4], γ‐Rb2[CO3], and γ‐Cs2[CO3] in P21/c; and δ‐K2[C2O4] and δ‐Rb2[C2O4] in Pbam. With respect to the centers of gravity of the oxalate and carbonate anions, respectively, the crystal structures of all known alkali‐metal oxalates and carbonates belong to the AlB2 family, and adopt either the AlB2 or the Ni2In arrangement depending on the size of the cation and the temperature. Despite the different sizes and constitutions of the carbonate and oxalate anions, the high‐temperature phases of the alkali‐metal carbonates M2[CO3] (M=K, Rb, Cs), exhibit the same sequence of basic structures as the corresponding alkali‐metal oxalates. The topological aspects and order–disorder phenomena at elevated temperature are discussed.
pH‐Responsive Shrinkage/Swelling of a Supramolecular Hydrogel Composed of Two Small Amphiphilic Molecules
Authors: Zhou Shan‐Lai , Matsumoto Shinji , Tian Huai‐Dong , Yamane Hiroki , Ojida Akio , Kiyonaka Shigeki , Hamachi Itaru
Published: December 2004

A pH‐responsive volume‐change function was successfully introduced into a supramolecular hydrogel that contained GalNAc‐appended (GalNAc=N‐acetylgalactosamine) glutamate ester 1 by the simple mixing of it with an appropriate amount of 2 a or 2 b amphiphilic carboxylic acid. In the 1:1 mixture (1:2), the hydrogel swelled under neutral pH conditions, but shrank to almost half of its original volume under acidic pH conditions. The structure and pH response of the mixed hydrogel were characterized by using X‐ray diffraction (XRD), confocal laser scanning microscopy (CLSM), transmission or scanning electron microscopy (TEM, SEM), and Fourier transform IR (FTIR) spectroscopy. Well‐developed fibers formed a stable hydrogel by self‐assembly, and under acidic conditions the charge of the carboxylic acid terminal (from the carboxylate anion) was neutralized and then these fibers became densely packed. This macroscopic pH response was also applied to the pH‐triggered release of bioactive substances. In this mixed supramolecular hydrogel, the hydrogelator 1 provides a stable hydrogel structure and the additive 2 acts as a commander that is sensitive to an environmental pH signal. The present supramolecular copolymerization strategy should be useful for the construction of novel, stimuli‐responsive, soft materials.
Conformational Dimorphism of 1,1,3,3,5,5‐Hexachloro‐1,3,5‐trigermacyclohexane: Solvent‐Induced Crystallization of a Metastable Polymorph Containing Boat‐Shaped Molecules
Authors: Ischenko Vladislav , Englert Ulli , Jansen Martin
Published: December 2004

Two crystalline modifications of 1,1,3,3,5,5‐hexachloro‐1,3,5‐trigermacyclohexane have been experimentally obtained as phase pure products and studied by single‐crystal X‐ray diffraction. The six‐membered heterocycles adopt a chair conformation in the α‐phase; this polymorph is accessible by crystallisation from solution and from the melt. In contrast, the β‐form is built up from boat‐shaped molecules; it can exclusively be crystallised fromn‐hexane. At the molecular level, formation energies of the 1,1,3,3,5,5‐hexachloro‐1,3,5‐trigermacyclohexane conformers have been compared by using molecular mechanics, semiempirical and ab‐initio quantum mechanical calculations. Possible reasons for the selective formation of the α‐ or β‐phase in specific solvents have been considered. Formation of the metastable phase is suggested to occur via a hypothetical intermediate of composition [(GeCl2CH2)3]⋅0.5 C6H14. For such an in‐silico solvate, a crystal structure of favourable lattice energy, closely related to the experimentally observed β‐modification, has been found through global energy minimisation. Elimination of then‐hexane molecules from this computer‐generated solid and subsequent simulated annealing resulted in a crystal structure that corresponds to the experimentally observed β‐phase within the limits of the force field calculations. This scenario implies solvent directed crystallisation of a metastable polymorphic molecular crystal.
Synthesis, Spectroscopic, and Electrochemical Studies of 1,2‐Naphthalene‐Ring‐Fused Tetraazachlorins, ‐bacteriochlorins, and ‐isobacteriochlorins: The Separation and Characterization of Structural Isomers
Authors: Makarova Elena A. , Fukuda Takamitsu , Luk′yanets Evgeny A. , Kobayashi Nagao
Published: December 2004

1,2‐Naphthalene‐ring‐expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2‐naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin‐layer chromatography (TLC) or high‐performance liquid chromatography (HPLC), and the structure of each isomer was determined by 1H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q‐band splits into two intense components similarly to the 2,3‐naphthalene‐fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene‐fused derivatives rather than the 2,3‐naphthalene‐fused derivatives. Molecular‐orbital and configuration‐interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations.
Zur Normung im Apparatebau
Authors: Heckmann C. J.
Published: December 2004

An zahlreichen Beispielen wird gezeigt, daß die Normung in der Verfahrenstechnik und im Apparatebau sich nicht allein auf Größe und Form von Flanschen, Rohren, Nieten und anderen Maschinenelementen beschränken darf, sondern daß sie zweckmäßigerweise auch ganze Apparaturen umfassen sollte.
Der Wärmeübergang in Rührgefäßen
Authors: Vdi H. Kraussold
Published: December 2004

Versuche über den Wärmeübergang in Rührgefäßen, vor längerer Zeit beim Werk Hoechst der ehemaligen I.G. Farbenindustrie A.G. durchgeführt

Die Versuche wurden auf Anregung von Dr.‐Ing. S. KießKalt in den Jahren 1935/38 unter Leitung des Verfassers durchgeführt. Die Messungen machten die herren Dipl.‐Ing. D. Bachmann, O. Kramer und F. Bieger.

, werden hier erstmals veröffentlicht und dabei verglichen mit Messungen über den Wärmeübergang an Modellapparaten von Chilton, Drew und Jebens bei der E. J. Du Pont de Nemours u. Comp., Wilmington, Del., sowie von Cummings und West bei der Rohm & Haas Comp., Philadelphia. Das Problem des Wärmeaustausches bei verschiedener Rührerdrehzahl und Temperatur ist nunmehr mit praktisch genügender Genauigkeit gelöst.
Beitrag zur Fischer‐Tropsch‐Synthese an Eisen‐Kontakten (Teil II)
Authors: Kölbel Herbert , Ackermann Paul , Ruschenburg Ernst , Langheim Robert , Engelhardt Friedrich
Published: December 2004

Für die Synthese am Eisenkatalysator sind die Art der Inbetriebnahme und die Betriebsbedingungen von ausschlaggebender Bedeutung. Es werden die Probleme der Formierung und der von den Betriebsbedingungen abhängigen Arbeitsweise des Katalysators dargelegt. Für drei der entwickelten Syntheseverfahren werden in zahlenmäßig belegten Beispielen die Ergebnisse und die Betriebsbedingungen mitgeteilt.
Einige Faustformeln zur Einstellung von Regelvorgängen
Authors: Oppelt Winfried
Published: December 2004

In den meisten Gebieten der chemischen Technik werden Regler und zu regelnde Anlagen von verschiedenen Herstellern geliefert. Dem Benutzer der Anlage bleibt dann die Aufgabe, beide Geräte aneinander so anzupassen, daß ein günstiges Zusammenwirken erzielt wird. Diese Aufgabe ist durch ‚Probieren’︁ allein im allgemeinen nicht zu lösen, auch der Betriebsingenieur benötigt hier die von der Theorie herkommenden Hinweise. Dieser Aufsatz gibt einige Faustformeln für die Einstellung von Reglern und zeigt ihre Anwendung.
Einfluß des Glockendurchmessers von Rektifizierböden auf ihre Wirkung und Belastbarkeit
Authors: Kirschbaum Emil
Published: December 2004

Der Durchmesser von Rektifiziersäulen mit Austauschböden wird allgemein mit Hilfe einer höchstzulässigen im leer gedachten Säulenquerschnitt herrschenden Dampfgeschwindigkeit bestimmt. Von letzterer ist bekannt, daß sie vom spez. Gewicht des Dampfes und der Flüssigkeit sowie vom Bodenabstand abhängt1. Es war aber unbekannt, ob der Glockendurchmesser selbst einen Einfluß auf die Höchstbelastung hat und welchen. An Hand von umfangreichen Versuchen, die mit einer Säule von 750 mm Dmr. durchgeführt wurden, wird nachgewiesen, daß nicht nur die zulässige Höchstbelastung, sondern auch die Wirkung der Austauschböden von der Abmessung und Zahl der Glocken entscheidend bedingt sind. Im Zusammenhang damit ist auch der Einfluß der verschiedenen konstruktiven Ausbildung des Glockenrandes sowie der Druckverlust in dem durch die Rektifizierböden strömenden Dampf untersucht worden

Die Tragweite der erhaltenen Ergebnisse entspricht dem Aufwand an Versuchseinrichtungen und Betriebskosten. Ihr finanzieller Wert ist der größte, der bisher zur Durchfüuhrung einer Forschungsarbeit im Laboratorium des Instituts für Apparatebau an der Techn. Hochhule Karlsruhe verzeichnet werden kann. Daß trotzdem die Arbeit durchgeführt werden konnte, ist der Unterstützung und Hilfe folgender Stellen zu verdanken:

Bertram Muller GmbH., Weidenau (Sieg),

DECHEMA (Deutsche Gesellschaft fur chemisches Apparatewesen) Frankfurt a. M.,

Adolf Messer GrnbH., Frankfurt a. M.,

Monopolverwaltung fur Branntwein, Karlsruhe,

Gebrüder Herrrnann, Köln‐Ehrenfeld,

Deutsche Kohlenbergbau‐Leitung, Essen,

Hochsrhulvereinigung. Karlsruhe,

Askania‐Werke, Berlin‐München,

Bad. Anilin‐ u. Sodafabrik AG., Ludwigshafen,

Dr.‐Ing. e. h. Hans Freudenberg, Weinheim.

Bei der Durrhfuhrung der Versuche waren unter Leitung und Mitarbeit d?s Verfasssrs folgende Herren tatig: Die Assistenten des Verfassers, die Herren Dr.‐Ing. H. Tifze, Dipl.‐Ing. H. Mende und Dipl.‐Ing. Fr. Hess, ferner die Herren Ing. Heinz Herrrnann, Dipl.‐Ing. G. Scholten und Dipl.‐ing. W. Dobmaier. Fur die Vorbereitung der Abbildungen bin ich meinem Assistenten, Herrn Dipl.‐Ing. Fr. Hess, dankbar.

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Interessante Entwicklungen aus der Verfahrenstechnik in USA
Authors: Miessner H.
Published: December 2004

Auf dem Gebiet der Verfahrenstechnik gibt es in Nordamerika eine ganze Reihe von Verfahren, die bisher in Deutschland noch nicht oder nur in ganz geringem Umfange eingeführt sind. Zum Teil handelt es sich dabei um Neuerungen, zum Teil aber auch um Verfahren, die bereits seit vielen Jahren in Amerika üblich, aus der ausländischen Literatur bekannt und trotzdem hier noch nicht übernommen sind. Auf Grund eigener Anschauung während einer mehrmonatigen Reise im Jahre 1950 wird nachfolgend über die Entwicklung in USA berichtet.
Keramische Werkstoffe für die chemische Technik
Authors: Miehr Wilhelm
Published: December 2004

Im folgenden werden die keramischen Werkstoffe für die chemische Technik nach Herstellung, Eigenschaften und Verwendung kurz beschrieben. Unterschieden werden feuerfeste und hochfeuerfeste Erzeugnisse, Steingut, Steinzeug, säure‐ und alkalibeständige Baustoffe, Quarzgut und Quarzglas, Kohlenstoff‐Erzeugnisse, Porzellan und Steatit. Die charakteristischen Kristallphasen als Träger der Güte keramischer Werkstoffe werden genannt. Abschließend werden einige Anwendungsbeispiele erwähnt.
Grundlagen der Wirbelschichtverfahren
Authors: Brötz Walter
Published: December 2004

Es wird an Hand von Photographien ein Überblick über das Verhalten von mit Gasen oder Flüssigkeiten aufgeströmten, gekörnten Schüttgütern gegeben. Auf Grund der vorliegenden Literatur und eigener Arbeiten werden quantitative Angaben gemacht über die Größe des Druckabfalles in Wirbelschichten, die minimalen und maximalen Geschwindigkeiten, bei denen eine Wirbelschicht noch beständig ist, und über die Schichtausdehnung infolge der Wirbelbewegung des gekörnten Gutes. Weitere Angaben folgen über die Viscosität in Wirbelschichten, den Böschungswinkel sowie den Stoff‐ und Wärmetransport, den Abrieb des wirbelnden Kornmaterials, die Erosion der Apparatewände sowie über chemische Umsetzungen in Wirbelschichten.
Strömungsformen und Wärmeübertragung in von Luft aufgewirbelten Schüttgutschichten
Authors: Wicke E. , Hedden S. K.
Published: December 2004

In der vorliegenden Arbeit werden Aufströmungseigenschaften und hydrodynamische Zustände mit Luft aufgewirbelter Partikelschichten untersucht. Anschliεßend wird eine Versuchsanordnung und Methode für Wärmeübergangs‐Messungen in solchen Schichten im Vergleich zu ruhenden Schüttungen behandelt und eine Deutung der Versuchsergebnisse gegeben.
Einiges über die Winkler‐Patente und ihre Erwirkung beim Reichspatentamt
Authors: Hubbuch W.
Published: December 2004

Es wird die Formulierung des Winkler‐Verfahrens in deutschen und amerikanischen Patentschriften erörtert, wobei wesentlich ist, daß die Vergasung in einer bewegten Schicht stattfindet.
Die Winklersche Wirbelschichttechnik
Authors: Sabel Franz
Published: December 2004

Eine Schicht von losem, feinkörnigem Schüttgut läßt sich in einem Behälter durch eine richtig dosierte Gasströmung in einen beweglichen Zustand versetzen. Die Schicht verhält sich dann ähnlich wie eine Flüssigkeit. Es werden Untersuchungen und Verfahren beschrieben, denen das Prinzip der Wirbelschicht zugrunde liegt.
Weiterentwicklung des Spiralwindsichters (Wirbelsichters)
Authors: Rumpf Hans , Kaiser Fritz
Published: December 2004

Aus dem bei der Badischen Anilin‐& Soda‐Fabrik, Ludwigshafen, entwickelten Spiralwindsichter entstand durch die Einführung rotierender Sichtraumwände, einer sich automatisch der Trenngrenze anpassenden Grobgutspülung und nach sorgfältiger konstruktiver Durcharbeitung eine betriebsreife Maschine. Bei dieser Entwicklung wurden neue Erkenntnisse über die Definition der Korngröße und das Ansatzverhalten von Feinstäuben gewonnen. Die vermutliche Weiterentwicklung wird abschließend skizziert.
Grundlagen einer wirtschaftlichen Gestaltung von Wärmeübertragern
Authors: Walger O.
Published: December 2004

Den zahlreichen Vorschlägen zur wirtschaftlichen Bewertung von Wärmeübertragern wird die Anregung entgegengestellt, die Kosten für den Gesamtaufwand an Rohrlänge zur wichtigsten Grundlage einer wirtschaftlichen Bewertung verschiedener Gestaltungen zu machen. Die Vergleiche werden für Längsstrom in Rohren und für Querstrom durch Rohrbündel mit Einschluß berippter Rohre in einheitlicher und systematischer Weise durchgeführt. Besonders bei niedrigen Re‐Zahlen erweisen sich Querstrom‐Anordnungen mit engen Rohrabständen als wirtschaftlich überlegen.
Erfahrungen mit dem Flammenphotometer nach Riehm‐Lange
Authors: Fischer J. , Zettler H.
Published: December 2004

Die Apparatur für die flammenphotometrische Bestimmung der Alkalimetalle, insbesondere des Lithiums, wird kritisch beschrieben. Störungen durch Grundsubstanz, Begleitelemente und Lösungsmittel werden untersucht. Angaben über zweckmäßige Arbeitsweise, Reproduzierbarkeit, Genauigkeit und Schnelligkeit der Methode werden gemacht. Ergebnisse von Amblygonit‐Analysen werden mitgeteilt.