bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical design equations for trickling‐filter process
Authors: Kong M. F. , Yang P. Y.
Published: December 2004

The concept of solid retention time (SRT) was applied in the trickling‐filter process. A rational model of the trickling‐filter process employing activated‐sludge‐process operational parameters was presented. The design equation was developed as follows; 1/SRT = [(S0 − Sn)/X]·(F/V)·Y − kd, where SRT is the sludge retention time, S0 is the influent substrate concentration; Sn is the effluent substrate concentration; X is the total cell mass retained per unit filter volume; V is the total volume of the filter; F is the influent flow rate; Y is the cell yield, and kd is the cell decay rate. A laboratory‐scale trickling‐filter pilot plant treating synthetic sucrose waste‐water was studied to verify the present design equation. The solid retention time was evaluated from the total slime mass (active and inactive) retained and the sludge wasted daily. It was found that the present design equation could be applied for designing the trickling‐filter process by the application of SRT employed in the activated sludge process. Also, the SRT could be related to the hydraulic loading and influent substrate concentration for a given filter medium. The variation of SRT by the hydraulic loading at constant organic loading was observed and could be expressed by the mechanistic model. When SRT was maintained more than 12 days, it provided the highest five‐day biological oxygen demand (BOD5) removal, minimum sludge production, and lowest sludge volume index (SVI) value. The present model does include both microbial growth kinetic concepts, which can be more practical and meaningful for the design of a trickling filter.
Immobilization of aminoacylase by adsorption to tannin immobilized on aminohexyl cellulose
Authors: Watanabe Taizo , Mori Takao , Tosa Tetsuya , Chibata Ichiro
Published: December 2004

The immobilization of aminoacylase (N‐acylamino acid amidohydrolase, EC 3.5.1.14) was investigated by using tannin immobilized on aminohexyl cellulose. The most active immobilized aminoacylase was obtained when aminoacylase was adsorbed to the immobilized tannin in a weak alkaline medium containing sodium chloride and n‐butanol at 37°C. The activity of the immobilized tannin–aminoacylase complex per unit volume was five times higher than that of the DEAE‐Sephadex–aminoacylase complex used for industrial production of L‐amino acids in our plants. The half‐life of the immobilized tannin–aminoacylase complex was 20 days under continuous operation at a high concentration of substrate; on the contrary, that of the DEAE‐Sephadex‐aminoacylase complex was 0.5 days.
Biomass recycling and species competition in continuous cultures
Authors: Weissman Joseph C. , Benemann John R.
Published: December 2004

A chemostat with cell feedback is analyzed for three kinds of limiting nutrient: a substrate dissolved in the inflow, a gas bubbled directly into the reactor, and light. The effects of recycle are distinct in each case, because the relationships between hydraulic detention time and nutrient inflow are different for each type of nutrient, Effluent recycle, in which the recycle stream is more dilute than the reactor, is discussed in terms of cell detention time and nutrient limitation. Results from chemostat cultures of the blue‐green alga, Spirulina geitleri, demonsrtat cell feedback under light limitation. Maximum Productivity is fixed by the incident light intensity. At a particular dilution rate recycling increases or decreases productivity by taking cell density closer or further from the optimum density. Cell recycle with heterogeneous populations can change the outcome of species competition. Selective recycling of one species can reverse this outcome or stabilize coexistence by its selective effect on cell detention time. Experimental results from light‐limited mixed cultures of S. geitleri and a Chlorella sp. verify this.
Immobilization and characterization of D–amino acid oxidase
Authors: Parkin Kirk , Hultin Herbert O.
Published: December 2004

Optimal conditions with respect to pH, concentration of glutaraldehyde and enzyme, and order of addition of enzyme and crosslinking reagent were established for the immobilization of hog kidney D‐amino acid oxidase to an attapulgite support. Yields of 40 to 70% were generally attained although when low concentrations of enzyme were used yields were consistently greater than 100%. It is suggested that this is due to a dimer → monomer shift at low protein concentrations. The stability of soluble D‐amino acid oxidase was dependent on the buffer in which it was stored (pyrophosphate‐phosphate >borate > Tris). Stability of immobilized enzyme was less than soluble in pyrophosphate‐phosphate buffer, but storage in the presence of FAD improved stability. In addition, treatment of stored, immobilized enzyme with FAD before assay restored some of its activity. The immobilized D‐amino acid oxidase was less stable to heat (50°C) than the soluble enzyme from pH 6 to 8 but was more stable above and below these values. Apparent km values for D‐alanine, D‐valine, and D‐tryptophan decreased for the immobilized enzyme compared to the soluble.
Identification of metabolic model: Citrate production from glucose by Candida lipolytica
Authors: Aiba Shuichi , Matsuoka Masayoshi
Published: December 2004

The concept of mass balance was used to analyze the metabolic pathways of citrate production by Candida lipolytica from glucose. Specific rates of glucose consumption, citrate and isocitrate productions, carbon dioxide evolution, and cellular syntheses of protein and carbohydrate were observed in an NH4+‐limited chemostat culture. These data permitted one to assess the carbon flux in vivo by solving simultaneous carbon balance equations with respect to intermediary metabolite pools in the steady State. Among the three models considered here, model I (which coordinates the pyruvate carboxylation with the tricarboxylic acid cycle, but disregards the glyoxylate cycle) was considered plausible because the carbon flux calculated so far was acceptable. On the other hand, models II and III (which overlook the pyruvate carboxylation and the 2‐oxoglutarate dehydrogenation, respectively) were found to be most unlikely because of the unusual flux assessed from these models.
Rapid ethanol fermentation of cellulose hydrolysate. I. Batch versus continuous systems
Authors: Ghose T. K. , Tyagi R. D.
Published: December 2004

Rapid fermentation of bagasse hydrolysate to ethanol under anaerobic conditions by a strain of Saccharomyces cerevisiae has been studied in batch and continuous cultures at pH 4.0 and 30°C temperature with cell recycle. By using a 23.6 g/liter cell concentration, a concentation of 9.7% (w/v)ethanol was developed in a period of 6 hr. The rate of fermentation was found to increase with supplementation of yeast vitamins in the hydrolysate. In continuous culture employing cell recycle and a 0.127 v/v/m air flow rate, a cell mass concentration of 48.5 g/liter has been achieved. The maximum fermentor productivity of ethanol obtained under these conditions was 32.0 g/liter/hr, which is nearly 7.5 times higher than the normal continuous process without cell recycle and air sparging. The ethanol productivity was found to decrease linearly with ethanol concentration. Conversion of glucose in the hydrolysate to ethanol was achieved with a yield of 95 to 97% of theoretical.
New nonsynthetic medium for Rhizobium culture production from wastes
Authors: Gulati S. L.
Published: December 2004

A nonsynthetic medium was formulated for placement of mannitol fully by saccharified pea husk (Pisum sativum L.) and water hyacinth (Eichhoornia crassipes) with Trichoderma viride QM 9414 and molasses. Yeast extract was Partially replaced by proteolysed pea husk, water hyacinth, and mycelium of T. viride QM 9414 by boiling 4 hr with 5% (v/v) HCl. The rhizobial growth was equal in both standard yeast extract mannitol (YEM) and formulated nonsynthetic media. However, barring Rhizobium phaseoli (urid) E‐6, the rhizobial counts in thenon‐synthetic medium were higher then the counts in YEM medium. In the fermentor, rhizobial growth was also almost equal to YEM medium. These results indicated that costly ingredients like mannitol and yeast extract can be replaced by hydrolysates of pea husk, water hyacinth, mycelium of T. viride, and molasses.
Use of an enzyme thermistor in continuous measurements and enzyme reactor control
Authors: Danielsson Bengt , Mattiasson Bo , Karlsson Roland , Winqvist Fredrik
Published: December 2004

The enzyme thermistor measures the heat produced by the action of an immobilized enzyme on a substrate present in the sample. Its application in analysis of discrete samples, e.g., in clinical chemistry, is well documented, but it has not been used so far for continuous measurements. We describe here the application of the enzyme thermistor for continuous monitoring and control of enzyme reactors. An enzyme thermistor filled with coimmobilized glucose oxidase and catalase was used to measure the amount of glucose in the outflow from a column reactor containging immobilized lactase acting on a lactose solution pumped through the reactor. The lactose conversion was kept on a constant level, irrespective of the actual enzymatic activity in the reactor, by regulating the flow through the reactor. The experiments were carried out with aqueous solutions of lactose as well as with whey from cow's milk.
Action of shear on enzymes: Studies with catalase and urease
Authors: Thomas C. R. , Dunnill P.
Published: December 2004

Intermittent shear was applied to approximately 1 mg/ml solutions of bovine liver catalase in a coaxial cylindrical viscometer at temperatures from 20 to 60°C and shear rates up to 683 sec−1. The viscometer was sealed to prevent evaporation. Up to 40°C there were no activity losses during 3 hr total shearing. Above 40°C shearing reduced losses due to thermal inactivation, possibly by interfering with precipitation. At 3440 sec−1 and 40°C fine precipitates formed but little activity was lost. No activity losses were found with experimental conditions under which Taylor vortexing occurred, nor when shear stresses were increased up 57 times by adding glycerol to raise the, viscosity. There were no significant losses in a capillary rheometer at shear rates up to 106 sec−1. When low concentration (6 μg/ml) catalase solutions were sheared there was little loss in sealed systems, but there were losses in “open” systems even in low‐temperature nonshear experiments. Although there were no losses with 1 mg/ml solutions, 6 μg/ml catalase solutions from an alternative source did lose activity in sealed systems but much less than expected from previously published work. Approximately 1 mg/ml jack bean urease solutions were sheared in the sealed system at 23°C and 683 sec−1 for 3 hr. No losses were found. No evidence of temporary or permanent inactivation was found with 28°g/ml solutions sheared in the presence of urea. Shear forces alone were not found to be as effective in causing enzyme inactivation as is generally believed and alternative mechanisms for damage are discussed.
Effect of pore diffusion limitation on dextrin hydrolysis by immobilized glucoamylase
Authors: Lee Douglas D. , Lee Gene K. , Reilly Peter J. , Lee Yoon Y.
Published: December 2004

Data reported here and previously indicate that when dextrin is hydrolyzed in the presence of immobilized glucoamylase, use of a larger average molecular weight substrate leads to lower overall rates of hydrolysis, while the maltose concentration during the bulk of the reaction and the maximum glucose concentration are lower than when the soluble form of the enzyme is employed under the same conditions. Computer simulation of the system demonstrated that all three observations were caused by pore diffusion limitation: the first by slow diffusion of substrate, the second by slow diffusion of intermediates, and the third by slow diffusion of glucose. Follow‐up experiments with glucoamylase immobilized to particles of different sizes confirmed this finding, as results with the smallest beads were identical to those with soluble glucoamylase.
Simple model for the energetics of growth on substrates with different degrees of reduction
Authors: Roels J. A.
Published: December 2004

A simple model is developed for the energy transformation in growing microbial systems. The model is based on a linear equation for ATP consumption in the processes of growth and maintenance. A combination of this equation with macroscopic balances for the various components, the systems exchanges with the environment, and application of the concepts of the elementary balance allow the derivation of linear equations for the exchange of substrate, oxygen, and carbon dioxide with the environment. For growth on one sole carbon and energy source the model allows the definition of a critical substrate yield are expected and below which is decreasing substrate yield and energy supply growth limitation are expected. This restriction can be interpreted in a variety of other ways. It supplies a rationale for non‐energy‐production‐coupled transfer of hydrogen to oxygen or wasteful expenditure of ATP in growth on highly reduced substrates. It also allows the formulation of a limit to the maximum yield on oxygen that can never be exceeded in growth on highly reduced substrates.
Immobilization of β‐galactosidase and other enzymes onto p‐amino‐carbanilated cellulose derivatives
Authors: Beddows C. G. , Mirauer R. A. , Guthrie J. T.
Published: December 2004

β‐Galactosidase and other enzymes were immobilized on p‐amino‐carbanilated derivatives of cellulose and methylol cellulose using the diazo method and through glutaraldehyde. The optimum conditions for coupling cellulose tri‐(p‐amino‐carbanilate) (CTAC) to β‐galactosidase were established. The diazo coupling method with CTAC gave greater activity than with glutaraldehyde when coupled to β‐galactosidase (Escherichia coli). The stability of the CTAC–β‐galactosidase system was examined. The disubstituted p‐amino‐carbanilate derivative (CDAC) gave a lower activity, whereas the methylol analog (MCTAC) gave slightly greater activity. The CTAC was also used to immobilize glucose oxidase, trypsin, pepsin, and papain.
Characteristics of hexadecane partition by the growth medium of Acinetobacter sp.
Authors: Käppeli O. , Finnerty W. R.
Published: December 2004

The partition of n‐hexadecane in the spent growth medium of Acinetobacter sp. HOI‐N was determined by measuring the increase in the relative aqueous solubility of 3H‐hexadecane as compared to controls. The amount of hexadecane partitioned was proportional to the protein concentration. The specific solubility of hexadecane (nmol/mg protein) was analyzed by least‐squares fitting yielding an average slope of 0.6 with a standard deviation of 0.3, indicating either nonequilibrium of hexadecane or physical aggregation of protein. The amount of hexadecane partitioned was concentration dependent yielding optically clear microemulsions at hexadecane concentrations of less than 1.4mM and macroemulsions at hexadecane concentrations of 1.4mM or greater. Preliminary results indicated that hexadecane and partitioned by a lipoprotein complex.
Immobilization and properties of Leuconostoc mesenteroids dextransucrase
Authors: Kaboli Hossein , Reilly Peter J.
Published: December 2004

Dextransucrase from Leuconostoc mesenteroides (NRRL B‐512F) was purified by ultrafiltration and gel filtration chromatography in 54% yield. The specific activity of a heart cut was 58.6 U/mg; cumulative purification of that preparation was 247−fold. Of 13 carriers surveyed, only alkylamine porous silica gave immobilization efficiencies consistently above 15 %. Immobilization to silica changed the properties of dextransucrase relatively little, the optimum pH for activity remaining at 5.2, while that for stability decreased from pH 5.5−6 to pH 5.2. In short assays, highest activities of both soluble and immobilized dextransucrase occurred at 30°C. Activation energies below that temperature were 8.6 kcal/mol for the former form and 1.7 kcal/mol for the latter. Maximum stabilization of soluble dextransucrase was attained by 5mM Ca2+.
Amperometric determination of choline with use of immobilized choline oxidase
Authors: Matsumoto Kunio , Seijo Hideji , Karube Isao , Suzuki Shuichi
Published: December 2004

Choline oxidase (choline: oxygen oxidoreductaserpar; was immobilized on a partially aminated polyacrylonitrile membrane. The enzyme electrode, consisting of an immobilized‐enzyme membrane and an oxygen probe, was employed for the determination choline. Dissolved oxygen consumption by the enzymatic reaction was measured amperometrically. The rate assay method was used for the choline determination. The response time of the sensor was 7 sec for choline. The choline assay was done within 1 min. The choline calibration curve was linear from 0 to 0.1mM. The response was reproducible within an average relative error of 2.3% when 0.2mM choline was employed for experiments. The choline in the fermentation media was determined by the sensor. Furthermore, phospholipids in the serum were also determined with native phospholiphase D and the enzyme electrode.
Ethanol production in an immobilized‐cell reactor
Authors: Sitton O. C. , Gaddy J. L.
Published: December 2004

Biomass can be converted to sugars by hydrolysis with enzymes or mineral acids. These sugars can be converted into a number of chemical intermediates in biological reactors. Biological reactions are generally slow and selection of the most efficient reactor is important in these applications. Immobilized‐cell reactors allow high cell densities and high throughput by attaching the microorganisms to a fixed support. This paper examines the rate of production of ethanol from glucose by Saccharomyces cerevisia in a packed column. These rates are compared with those for the same reaction in a stirred reactor.
Production of the macrolide antibiotic tylosin in batch and chemostat cultures
Authors: Gray P. P. , Bhuwapathanapun S.
Published: December 2004

The production of tylosin and related compounds by Streptomyces fradiae NRRL 2702 was studied in batch and chemostat cultures using a soluble synthetic medium. In batch culture, a trophophase–idiophase kinetic pattern was observed with tylosin, macrocin, and relomycin accumulating in the idiophase. When the organism was grown in chemostat culture, the specific rate of production of tylosin and related compounds (qtylosin) was found to be a function of the growth rate. The maximum value of (qtylosin) was observed when D = 0.017 hr−1. At this growth rate only tylosin and relomycin accumulated in the medium. By varying the concentration of glucose in the ingoing medium it was possible to study the effects of glucose on tylosin synthesis in chemostat cultures. At a growth rate of 0.017 hr−1, the maximum value of qtylosin was 0.71 mg tylosin/g dry weight (DW)/hr when the glucose uptake rate was 7 mg glucose/g DW‐hr. This value of qtylosin was 40% greater than the maximum qtylosin observed in batch culture. When glycerol was substituted for glucose in the medium, it was possible in chemostat culutures to get values of qtylosin approximately 20% greater than those obtained with glucose at the same uptake rate. By varying the concentration of sodium glutamate in the ingoing medium it was possible to show that increasing the specific uptake rate of sodium glutamate increased the values of qtylosin obtained. Similar chemostat experiments where the inorganic phosphate concentration in the ingoing medium was varied showed that increased the uptake of phosphate decreased the values of qtylosin obtained. Also increasing the uptake rate of phosphate increased the relomycin‐to‐tylosin ratio. By taking into consideration the suppressing effects of glucose and the stimulating effects of sodium glutamate on tylosin synthesis, it was possible to formulate a medium that resulted in a value of qtylosin of 1.1 mg/g/hr being obtained at a growth rate of 0.03 hr−1. Batch fermentations with this medium did not follow a trophophase–idiophase kinetic pattern, but instead tylosin was actively synthesized during a period of rapid mycelial growth.
A quantitative description of the growth of Saccharomyces cerevisiae CBS 426 on a mixed substrate of glucose and ethanol
Authors: Geurts Th. G. E. , De Kok Hermine E. , Roels J. A.
Published: December 2004

Saccharomyces cerevisiae CBS 426 was grown aerobically in continuous culture with a mixture of glucose and ethanol as the carbon source. The flows of biomass, glucose, ethanol, oxygen, and carbon dioxide were measured. A model for growth with two substrates was derived. Application of this model to the above‐mentioned system yielded values for YATP and P/O. The joint confidence regions for these parameters were calculated. The relevance to industrial production of bakers' yeast is discussed.
Preparation and characterization of enzymes immobilized by graft copolymerization to different polysaccharides
Authors: D'Angiuro L. , Cremonesi P. , Mazzola G. , Focher B. , Vecchio G.
Published: December 2004

A method of enzyme immobilization by graft copolymerization on polysaccharides is reported. Glycidylmethacrylate was used as a vinylating reagent and the reaction product with enzymes (HRP, GOD, Am, ChT) was copolymerized with different matrices (cellulose, Sepharose, Sephadex, Starch). Various factors affect the final activity of copolymers; these include the redox system, the type of support, and the quantity and type of vinyl monomer added. Using a fixed quantity of enzyme and support (3 mg enzyme, 100 mg support), the coupling efficiency varied from 2 to 50%. The most important characteristics in these immobilized systems were tested (stability in continuous washing, kinetic characteristics, storage, thermal, and lyophilization stability). Immobilized‐enzyme graft copolymers have very similar kinetic behavior to that of the free enzyme. Diffusion is not seriously limited, as shown by kinetic parameters and energy activation values, and this indicates that the immobilization reaction does not alter the enzymatic activity.
Kinetic studies of cellodextrins hydrolyses by exocellulase from Trichoderma reesei
Authors: Hsu Teh‐An , Gong Cheng‐Shung , Tsao George T.
Published: December 2004

The kinetics of the hydrolyses of cellotriose and of cellotetraose by cellobiohydrolase were studied using a convenient integral technique. Reaction mechanisms and mathematical models were postulated to describe the reactions. The end‐products of the reaction were found to be inhibitory toward hydrolysis in a competitive mode. Hydrolysis of cellotetraose produces cellobiose and hydrolysis of cellotriose produces cellobiose and glucose. Both sugars inhibit the enzyme with cellobiose being a stronger inhibitor.
Concentration of proteins by foaming
Authors: Lalchev Zdr. , Exerowa D.
Published: December 2004

Factors influencing foam concentration of proteins are studied. Projecting practical application of the results, the possibilities for obtaining good enrichment ratio are studied. The dependencies of enrichment ratio and albumin concentration in the foam on the initial solution concentration and expansion factor are investigated. Using a method of application of pressure difference in the Plateau‐Gibbs borders of the foam, stabilized by albumin and lysozyme, comparatively high enrichment ratio of the proteins is obtained. The method is applicable for any protein foams and is more effective for more stable foams. The enrichment ratio of albumin significantly depends on the parameters and properties of the foam (dispersion, expansion factor, stability, etc). and also on the initial concentration of the solution. The protein concentration in the foam and the foam dispersion depend in a different way on the initial concentration by the creation of pressure difference in the foam and the Rf/C0 dependence shows a maximum. The latter indicates the existence of an optimum of the initial protein concentration with respect to the efficiency of the foam concentration and the foam separation of proteins from solutions.
Self‐cleaning membranes for ultrafiltration
Authors: Velicangil O. , Howell J. A.
Published: December 2004

In order to reduce the severe flux losses encountered during ultrafiltration of protein solutions, proteases were immobilized on Ultrafiltration membranes to hydrolyze the deposited solute molecules. Over a standard 22 hr run 25 to 78% improvement in cumulative permeate yield was obtained when processing 0.5% albumin or hemoglobin. It was also demonstrated that the flux enhancements were due to the biochemical action of the absorbed protease and not to its physical effect as a prefilter coat. with the aid of a model retardation of gel formation mechanism was demonstrated. Economics of the system were shown to be favorable, improving the rate of return on capital investment up to 50% by reduction of the total membrane area of the plant.
Continuous cell propagation using low‐charge microcarriers
Authors: Crespi Charles L. , Thilly William G.
Published: December 2004

Microcarrier cell culture technology has been extended by the finding that two mammalian epithelial cell lines can be continuously subcultured by simple bead‐to‐bead transfer in normal medium in which calcium concentrations have been reduced. Data are reported which show that the hamster ovary line CHO‐Kl and the monkey kidney line LLC‐MK2 can be subcultured simply by adding fresh microcarriers to the stirred suspension culture. Thirteen generations of continuous exponential growth are demonstrated with two such subcultures for the CHO‐Kl cells and with four such subcultures for the LLC‐MK2 cells. Cell generation times were unchanged by this subculturing approach compared to standard subculturing procedure using trypsin to remove cells from surfaces. We have applied this technique to the production of vesicular stomatitis virus (VSV) from CHO‐Kl cells. Viral yields were comparable (less than twofold difference) in microcarrier cultures which were subcultured via bead‐to‐bead transfer or by the standard means of removing cells from microcarriers with trypsin.
Enhancement of oxygen absorption by magnetite‐containing beads of immobilized glucose oxidase
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki
Published: December 2004

Rates of oxygen absorption into glucose solutions were measured using an immobilized‐enzyme reactor, in which magnetite‐containing beads of immobilized glucose oxidase were moved by a revolving magnetic field to reduce the mass transfer resistances at the gas–liquid interface and around the bead. Data were also obtained for oxygen absorption into glucose solutions containing soluble or immobilized glucose oxidase (without magnetite), as well as for physical absorption of oxygen. The rates of physical absorption for the runs with the magnetite‐containing beads increased because of mechanical stirring caused by spinning of the beads at the gas‐liquid interface. In this case the experimental enhancement factors were found to be larger than those predicted on the basis of the film theory for gas absorption with a pseudo‐first order reaction.
Application of the macroscopic electric charge balance in fermentation modeling
Authors: Heijnen J. J.
Published: December 2004

This article treats the application of the macroscopic electric charge balance in fermentation modeling. From the presented calculations it follows that the definition formula of the so‐called degree of reduction is changed due to the ionic character of the fermentation reactants. It is also shown that the macroscopic electric charge balance, together with the ionic equilibria between fermentation reactants, leads to an expression for the calculation of the pH during fermentation. Finally it is concluded that one should be very careful in the estimation of biomass production from the acid or base feed rates which are necessary for pH control.
Mechanism of inhibition caused by long‐chain fatty acids in anaerobic digestion process
Authors: Hanaki Keisuke , Matsuo Tomonori , Nagase Michihiko
Published: December 2004

The inhibitory effect of long‐chain fatty acids on the anaerobic digestion process was examined in batch experiments using synthetic substrates. The addition of long‐chain fatty acids caused the appearance of the appearance of the lag period in the methane production from acetate and in the degradation of both long‐chain fatty acids and n‐butyrate. Methane production from hydrogen proceeded without lag period although its rate was lowered. Fermentation of glucose was not inhibited. Neutral fat in the whole milk was easily hydrolyzed to long‐chain fatty acids, which brought about the inhibition. The addition of calcium chloride reduced the inhibitory effect of long‐chain fatty but it did not do so after the culture had been exposed to long‐chain fatty acids for more than several hours. The addition of calcium carbonate could not reduce the inhibition because of its insolubility.
Comparison of different methods of glucose oxidase immobilization
Authors: Valentová O. , Marek M. , Švec F. , Štamberg J. , Vodrážka Z.
Published: December 2004

Glucose oxidase was immobilized by covalent bond to two basic types of sorbents—glycidylmethacrylate copolymers and bead cellulose. These two types of carries were chemically modified, if needed, by the employing various procedures and subsequently used in the immobilization of native and oxidized glucose oxidase. The samples thus obtained were compared with those of immobilized glucose oxidase bound onto some common carriers. Samples which possessed not only a high absolute activity but also adequate mechanical and flow properties were characterized in greater detail with respect to the immobilization efficiency and kinetic properties of bound glucose oxidase.
Kinetics of biomass formation and citric acid production by Aspergillus niger on pilot plant scale
Authors: Roehr Max , Zehentgruber Otto , Kubicek Christian P.
Published: December 2004

Citric acid fermentation on pilot plant scale was studied, using two strains of Aspergillus niger of different productivity. Growth and product formation were analyzed from a high number of data points. Several phases could be distinguished which were described by a sequence of logarithmic, cube‐root, and linear equations. Growth and product formation could be related by a modified Luedeking‐Piret equation, taking into consideration a lag time for the organism to shift to shift into the physiological state ready for product formation. The observed differences in productivity of the two strains are reflected by the different non‐growth‐associated terms of the equation. In light of these findings the classical "type II fermentation" is redefined as a mixed type–resembling type I during trophophase and type III during idiophases.
Application of porous teflon tubing method to automatic fed‐batch culture of microorganisms. I. Mass transfer through porous teflon tubing
Authors: Yamané Tsuneo , Matsuda Morio , Sada Eizo
Published: December 2004

For the purpose of a rational design for an automatic feedback control system incorporating a porous Teflon tubing sensor in semibatch culture, steady‐state mass‐transfer characteristics of tubing sensors have been investigated theoretically and experimentally, and also dynamic responses have been studied experimentally. A distributed mathematical model for steady‐state diffusion has been solved numerically and its solution has been shown as useful for the sensor design. The overall mass‐transfer resistance of radial diffusion has been shown to be the sum of external liquid‐film mass‐transfer resistance and membrane diffusion resistance. The steady‐state experiments using ethanol dissolved in water revealed that its transfer into the tubing was controlled by the molecular diffusion within the tubing‐wall membrane. Oxygen transfer from external water into the tubing was shown experimentally to be controlled by the liquid‐film resistance outside the tubing. In general, the radial mass transfer of a substance having a small Henry's constant is controlled by the liquid‐film resistance.

The response of the tubing sensor‐detector‐recorder system for the stepwise addition of ethanol into the external water could not be represented by a simple combined system of the first‐order delay with lag time. The responses depend on the characteristics of the tubing as well as flow rate of the carrier gas, etc., but they were quite excellent in all cases (e.g., 90% in 20 s).
Microcalorimetric study of aerobic growth of Escherichia coli in batch culture
Authors: Ishikawa Yasufumi , Nonoyama Yukio , Shoda Makoto
Published: December 2004

Thermograms of an aerobic batch culture of Escherichia coli K‐12 in synthetic medium were obtained by using a newly designed mecrocalorimeter. The thermograms reflected sharp changes of metabolic activity in glucose‐, nitrogen‐, or oxygen‐limited cultures. The thermo chemical analysis for each culture condition was done using the data of the heat evolved, the head of combustion of cells, and the elementary analysis of the cells. The efficiency of energy conversion determined experimentally revealed nutritional differences.
Hydrocracking of the oils of Botryococcus braunii to transport fuels
Authors: Hillen L. W. , Pollard G. , Wake L. V. , White N.
Published: December 2004

Hydrocarbon oils of the alga Botryococcus braunii, extracted from a natural “bloom” of the plant, have been hydrocracked to produce a distillate comprising 67% gasoline fraction, 15% aviation turbine fuel fraction, 15% diesel fuel fraction, and 3% residual oil. The distillate was examined by a number of standard petroleum industry test methods. This preliminary investigation indicates that the oils of B. braunii are suitable as a feedstock material for hydrocracking to transport fuels.
Continuous ethanol production and cell growth in an immobilized‐cell bioreactor employing Zymomonas mobilis
Authors: Arcuri E. J.
Published: December 2004

Ethanol‐producing bioreactors employing cells of Zymomonas mobilis attached to glass‐fiber pads were operated continuously for as long as 28 days. Ethanol production, which is related to bed‐associated biomass levels, was found to occur in three distinct phases: an exponential phase, a linear phase, and a “steady‐state” phase. After prolonged operation, a bacterial floc developed in the reactor. The maximum effluent ethanol concentration and the maximum volumetric productivity were 6.4% and 152 g L−1 h−1, respectively, and both were attained at a liquid residence time of from 10–15 min. Both maxima occurred after the development of the bacterial floc. The flocculant bacterium has been isolated and tentatively identified as a flocculant strain of Z. mobilis.
Effect of nitrogen‐mediated changes in alkalinity on pH control and CO2 supply in intensive microalgal cultures
Authors: Goldman Joel C. , Dennett Mark R. , Riley Carol B.
Published: December 2004

The freshwater alga Scenedesmus obliquus was grown in continuous culture at a fixed dilution rate of 0.5/day, but at varying pH in the range 4.17–10.67. The pH was regulated in the range 4.17–7.67 by continuously bubbling 1% CO2‐enriched air into the cultures and by varying the source of nitrogen (NO, NH, or urea) in the growth medium, which, in turn, led to changes in culture alkalinity. Culture alkalinity and P were the sole determinants of pH. A pH‐stat system, together with NO in the medium, was used to regulate the pH in the range 7.92–10.67. Maximum productivity, which occurred at pH 6.6, was dependent on N source only to the extent that culture alkalinity was a function of nitrogen uptake. The results demonstrate that the choice of N is a critical factor in controlling the pH of large‐scale algal cultures. NH is a poor source of N because it leads to destruction of culture alkalinity and concomitant growth‐inhibiting reductions in pH, whereas NO has an opposite effect, although pH is not so severely affected in this case. Urea is, by far, the most suitable N source for maximizing algal yield when it is supplied in combination with the proper amounts of HCO alkalinity in the growth medium and percent CO2 in the bubbled gas that will lead to an equilibrium pH near the optimum pH.
Kinetic study of sulfide leaching by galvanic interaction between chalcopyrite, pyrite, and sphalerite in the presence of T. ferrooxidans(30°C) and a thermophilic microorganism (55°C)
Authors: Mehta A. P. , Murr L. E.
Published: December 2004

A systematic, kinetic study and comparison of the leaching of mixed metal sulfides by galvanic conversion and in the presence of bacteria has been carried out for the first time using both powder (−100 to −400 mesh) and larger (bulk) specimen systems. The rates of dissolution of copper from chalcopyrite and zinc from sphalerite as single, electrically isolated (separate) systems were compared with electrically contacting (galvanically coupled) systems involving CuFeS2/FeS2 and ZnS/FeS2, with and without bacteria and at temperatures of 30 and 55°C. The dissolution of Cu was observed to increase by a factor of 4.6 when the galvanic leaching of CuFeS2/FeS2 was compared to CuFeS2 leaching at 30°C. When bacteria were present, Cu dissolution increased by an additional factor of 2.1 in the CuFeS2/FeS2 system. At 55°C, the corresponding ratios for Cu were 4.3 and 2.7, respectively. The galvanic leaching of Zn in the ZnS/FeS2 system compared to ZnS leaching increased by a factor of 2 at 30°C; in the presence of bacteria the dissolution of Zn from the ZnS/FeS2 system increased by an additional factor of 1.3 at the same temperature. By comparison, the ratio of Cu dissolution from CuFeS2 in acid‐bacterial medium and sterile controls (without bacteria) was 5.5. The corresponding ratio for Zn from ZnS was 2.2 at both 30 and 55°C. The order of reaction was found to be essentially first order for the leaching of powder systems at both 30 and 55°C (with T. Ferrooxidans and thermophilic microorganisms, respectively). The corresponding reaction rate constants were observed to be 12.6 and 22.9 for T. ferrooxidans and the thermophilic microorganisms, respectively. Activation energies for the various systems were also determined.
Activated sludge treatment of synthetic wastewater containing pentachlorophenol
Authors: Edgehill Richard U. , Finn Robert K.
Published: December 2004

Activated sludge treatment of a pentachlorophenol (PCP)‐containing synthetic waste was examined. With a waste containing some sugars, and 40–120 mg/L PCP, laboratory activated sludge required about seven days for acclimation. However, the prior addition of a quasipure culture of PCP‐metabolizing Arthrobacter resulted in immediate acclimation. Even with acclimated sludge, however, the system was upset for two days by a simple step change from 40 to 120 mg/L of PCP. The stability of the system to such a shock load was considerably improved when a chemostat culture of the PCP‐metabolizing Arthrobacter was fed slowly into the mixed liquor. Kinetic models were developed to describe the dynamic response of the system in terms of growth parameters, hydraulic detention time, sludge age, and bleed‐in rate from the chemostat.
Application of macroscopic balances to the identification of gross measurement errors
Authors: Wang Nam Sun , Stephanopoulos Gregory
Published: December 2004

A systematic method is presented which is capable of both detecting the presence of grossly biased measurement errors and locating the source of these errors in a bioreactor through statistical hypothesis testing. Equality constraints derived from material and energy balances are employed for the detection of data inconsistencies and for the subsequent identification of the suspect measurements by a process of data analysis and rectification. Maximum likelihood techniques are applied to the estimation of the states and parameters of the bioreactor after the suspect measurements have been eliminated. The level of significance is specified by the experimenter while the measurments are assumed to be randomly, normally distributed with zero mean and known variances. Two different approaches of data analysis, batchwise and sequential, that lead to a consistent set of adjustments on the experimental values, are discussed. Several examples based on the fermentation data taken from literature sources are presented to demonstrate the utility of the proposed method, and one set of data is solved numerically to illustrate the computational aspect of the algorithm.
Ethanol fermentation in a yeast immobilized tubular fermentor
Authors: Gencer M. A. , Mutharasan R.
Published: December 2004

In this article, a mathematical model describing the kinetics of ethanol fermentation in a whole cell immobilized tubular fermentor is proposed. Experimental results show reasonable agreement with the proposed model. A procedure for treating the fermentation data for determining the ethanol inhibition constants k1 and k2 is described. The ethanol productivity of the immobilized cell fermentor is compared with those of traditional fermentors. Experimental studies indicate that with Saccharomyces cerevisiae (NRRL Y132) culture, ethanol productivity in the range 21.2–83.7 g ethanol L−1 h−1 at ethanol concentration of 76–60 g/L can be achieved. This is comparable to or higher than those reported in the literature for yeast. The product yield factor of 0.5 g ethanol/g glucose was obtained. The immobilized cell fermentor does not show washout at dilution rates of 7 h−1 and shows good stability over a 650‐h operating period.
Kinetics of formation of maltose and isomaltose through condensation of glucose by glucoamylase
Authors: Adachi Shuji , Ueda Yasuo , Hashimoto Kenji
Published: December 2004

A kinetic model was devised for the hydrolysis and synthesis of maltose and isomaltose by two glucoamylases from Rhizopus niveus and Aspergillus niger, and the validity of the model was verified experimentally at 313 K and pH 5.0. For both enzymes, the formations of maltose and isomaltose from glucose were parallel reversible reactions, and glucosyl transfer between maltose and isomaltose was not observed. The enzymes catalyzed rapid hydrolysis and synthesis of maltose. Isomaltose was hydrolyzed and synthesized more slowly, but the level produced from glucose was much higher than that of maltose. These hydrolysis and condensation reactions were expressed well by the model.
Equations and calculations for fermentations of butyric acid bacteria
Authors: Papoutsakis Eleftherios Terry
Published: December 2004

A stoichiometric equation has been derived which describes the interrelations among the various products and biomass in fermentations of butyric acid bacteria. The derivation of the equation is based on an assumed ATP yield, two biological regularities, and the biochemistry of product formation of the fermentations. The equation obeys the constraints imposed on growth and product formation by thermodynamics and the biochemical topology. The validity of the equation is tested using a variety of fermentation data from the literature. The uses, improvements, limitations, and extensions of the equation are also discussed in detail. For example, the fermentation equation is used to calculate the maximal possible yields of the main fermentation products.
The growth of Saccharomyces cerevisiae CBS 426 on mixtures of glucose and succinic acid: A model
Authors: Bonnet J. A. B. A. F. , Koellmann C. J. W. , Dekkers‐de Kok Hermine E. , Roels J. A.
Published: December 2004

Saccharomyces cerevisiae CBS 426 was grown in continuous culture in a defined medium with a mixture of glucose and succinic acid as the carbon source. Growth on succinic acid was possible after long adaptation periods. The flows of glucose, succinic acid, oxygen, carbon dioxide, and biomass to and from the system were measured. It proved necessary to expand our previous model to accommodate the active transport of succinic acid by the cell. The values found for the efficiency of the oxidative phosphorylation (P/O) and the amount of ATP needed for production of biomass from monomers gave the same values as found for substrate mixtures taken up passively.
Purification and some properties of pure Cochliobolus lunatus fibrinolytic Enzyme
Authors: Abdel‐Fattah Ahmed F. , Ismail Abdel‐Mohsen S.
Published: December 2004

Purification of partially purified fibrinolytic enzyme was attempted by chromatography on DEAE‐cellulose (D‐52) column. The results indicated the resolution of three protein components and one minor component. It was shown that the first component was the major of the applied sample. Examination of fibrinolytic activity of the different fractions of components one and two indicated that only the first component possessed fibrinolytic activity. Fibrinolytic activity of the applied sample was completely recovered by the first enzyme component, and the most active fraction of this enzyme component showed 3.3‐fold purification. The pure fibrinolytic enzyme was relatively more stable at pH 6.98, which was also optimal for its activity. After heating the enzyme solution (pH = 6.98) at 55 and 60°C for 15 min, the enzyme still retained 34.7 and 17.3% of its original activity, respectively. Zinc ions partially inhibited the enzyme. Copper ions activated the enzyme. Iodine partially inhibited the fungal fibrinolytic enzyme at a final concentration of 10−4M; at 10−2M complete inactivation was brought about. The p‐chloromercuribenzoate at a final concentration of 10−2M brought about partial inhibition whereby the enzyme lost about 33% of its original activity. Reduced glutathione brought about activation of the enzyme, while trypsin inhibitor did not show any effect on enzyme activity.
Competitive adsorption of cellulase components and its significance in a synergistic mechanism
Authors: Ryu Dewey D. Y. , Kim Cheol , Mandels M.
Published: December 2004

Some studies on the adsorption of cellulase on cellulose revealed part of the mechanisms involved in the enzymatic hydrolysis of cellulose and provided some clues to the synergistic mechanism of cellulase complex. The adsorption of cellulase was significantly affected by the reaction conditions and physical chemical characteristics of cellulose. Endoglucanase consisted of adsorbable and nonadsorbable components. Cellobiohydrolase had the strongest adsorption affinity. Each cellulase component is postulated to have distinctly different adsorption sites on cellulose, corresponding to the active sites in the hydrolysis reaction. Competitive adsorption kinetics between cellulase components were also observed during the adsorption process. The degree of competitive adsorption was most remarkable when the composition of cellulase components was nearly the same as that in the crude cellulase complex. This seems to show the optimal relative composition of cellulase components. The synergism between cellobiohydrolase and endoglucananse could be elucidated more clearly by this competitive adsorption model of the reaction mechanism.
Acid phosphatase deactivation by a series mechanism
Authors: Gianfreda Liliana , Marrucci Giuseppe , Grizzuti Nino , Greco Guido
Published: December 2004

Acid phosphatase (E.C.3.1.3.2.) thermal deactivation at pH 3.77 has been investigated by monitoring the enzyme activity as a function of time in the hydrolysis of p‐nitrophenyl phosphate. The experimental curves obtained show a two‐slope behavior in a log (activity)versus‐time plot, which indicates that deactivation occurs via a complex mechanism. From the dependence of the kinetic parameters on both deactivation and hydrolysis temperatures, it is inferred that the deactivation mechanism involves intermediate, temperature‐dependent, less‐active forms of the enzyme. This interpretation is confirmed by the results of additional tests in which the temperature was suddenly changed during the deactivation process.