bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the hydrolysis of lean meat protein by alcalase: Derivation of two alternative rate equations and their fit to experimental data
Authors: O'Meara G. M. , Munro P. A. 
Published: December 2004

AbstractTwo rate equations have been developed to model the hydrolysis of ground lean meat protein by Alcalase. The first equation was based on classical Michaelis‐Menten kinetics and the second on the adsorption of enzyme to the protein prior to reaction. It was assumed that this adsorption could be modelled by a Langmuir‐type adsorption isotherm. Each equation considered the enzyme to be competitively inhibited by reaction product, and considered enzyme inactivation to be first order. Both rate equations have been fitted to experimental data obtained from the hydrolysis of meat protein by Alcalase. Initial rate data indicated that the adsorption model was more appropriate. However, both equations gave satisfactory fits to 11 reaction progress curves determined over a wide range of enzyme and substrate concentrations.
Series mechanism of enzyme deactivation. Characterization of intermediate forms
Authors: Gianfreda Liliana , Marrucci Giuseppe , Grizzuti Nino , Greco Guido 
Published: December 2004

AbstractAcid phosphatase (E.C. 3.1.3.2) undergoes complex thermal deactivation phenomena, as revealed by the two‐slope pattern of the enzyme logarithmic‐specific‐activity versus time curves. The native enzyme first decays toward an equilibrium distribution of less, but still active, intermediate structures and these, in turn, undergo a final degradation to a completely inactive form. The effect of the experimental conditions at which the enzyme is kept during the deactivation process on the characteristics of these intermediate enzymatic structures has been investigated. The kinetic parameters of p‐nitro‐phenyl phosphate hydrolysis, as catalyzed by some of these intermediate forms, have been determined and the results compared to those obtained with the native enzyme.
Enzyme adsorption in porous supports: Local thermodynamic equilibrium model
Authors: Pedersen Henrik , Furler Larry , Venkatasubramanian K. , Prenosil Jiri , Stuker Ernst 
Published: December 2004

AbstractEnzyme adsorption from a finite bath (batch adsorption) onto porous spherical supports is investigated both experimentally and theoretically using β‐galactosidase and Duolite ion‐exchange resin as a model system. Efficient numerical techniques are presented that have been used in conjunction with a parameter estimation routine to evaluate adsorption isotherm constants. Results show that even for adsorption processes lasting almost 10 h, the majority of the enzyme is confined to the outer half of the support and, for high initial enzyme concentrations in the bath, this loading takes place as a slowly moving front. Information on the enzyme distribution has practical importance in the design of immobilized enzyme reactors that in previous works have almost always been analyzed assuming a uniform catalyst distribution.
Steady‐state and transient behavior in microbial methanification: I. Experimental results
Authors: Bhatia D. , Vieth W. R. , Venkatasubramanian K. 
Published: December 2004

AbstractThe process of methanification of volatile fatty acids (VFA) was studied to elucidate its kinetics. An upflow anaerobic sludge bed (UASB) system was used to perform the experiments. At residence times of less than 2.5 h the UASB system was found to exhibit hysteresis with respect to acetic and propionic acid consumption but not with respect to butyric acid consumption. These hysteretic effects could be attributed to the manner in which the various VFA‐consuming cultures were structured inside the flocculated biomass in light of the cross‐inhibitory effects of the acetic‐ and propionic‐acid‐consuming fractions of the total culture. (Butyric acid proved to be non‐interactive.) Production of methane was found to respond almost instantaneously to changes in the inlet conditions of the UASB system. This indicated that methane is not primarily growth associated, as has often been assumed, but is related to changes in the culture's maintenance energy requirements. Reactor operation was found to be stable even when the concentration of each VFA in the feed was simultaneously changed by 50%. Even at very high organic throughput rates (35 kg COD/day m3‐reactor) conversions of 82% were observed.
Role of cometabolism in biological oxidation of synthetic compounds
Authors: Venkataramani E. S. , Ahlert R. C. 
Published: December 2004

AbstractA significant portion of the total biodegradative activity toward synthetic compounds may involve cometabolism; thus, the latter represents an important type of microbial process. A mixed microbial population acclimated to highstrength industrial wastewater degraded about 90% of the organic carbon present in the wastewater. A reasonable agreement in the carbon balance provided clear evidence for the biodegradability of residual organic species. Based on the growth expression of Haldane to account for substrate inhibition, a substrate utilization model to quantify the role of cometabolism coupled with cellular maintenance is proposed. The kinetic parameters of the model have been estimated from experimental data. If the maintenance values are assumed negligible, as has been observed for wastewater systems, it is possible to quantify the magnitude of co‐metabolism encountered in the biological oxidation of synthetic organic compounds.
Recycle of enzymes and substrate following enzymatic hydrolysis of steam‐pretreated aspenwood
Authors: Mes‐Hartree M. , Hogan C. M. , Saddler J. N. 
Published: December 2004

AbstractThe commercial production of chemicals and fuels from lignocellulosic residues by enzymatic means still requires considerable research on both the technical and economic aspects. Two technical problems that have been identified as requiring further research are the recycle of the enzymes used in hydrolysis and the reuse of the re calcitrant cellulose remaining after incomplete hydrolysis. Enzyme recycle is required to lower the cost of the enzymes, while the reuse of the spent cellulose will lower the feedstock cost. The conversion process studied was a combined enzymatic hydrolysis and fermentation (CHF) procedure that utilized the cellulolytic enzymes derived from the fungus Trichoderma harzianum E58 and the yeast Saccharomyces cerevisiae. The rate and extent of hydrolysis and ethanol production was monitored as was the activity and hydrolytic potential of the enzymes remaining in the filtrate after the hydrolysis period. When a commercial cellulose was used as the substrate for a routine 2‐day CHF process, 60% of the original treated, water‐extracted aspenwood was used as the substrate, only 13% of the original filter paper activity was detected after a similar procedure. The combination of 60% spent enzymes with 40% fresh enzymes resulted in the production of 30% less reducing sugars than the original enzyme mixture. Since 100% hydrolysis of the cellulose portion is seldom accomplished in an enzymatic hydrolysis pro cess, the residual cellulose was used as a substrate for the growth of T. harzianum E58 and production of celulolytic enzymes. The residue remaining after the CHF process was used as a substrate for the production of the cellulolytic enzymes. The production of enzymes from the residue of the Solka Floc hydrolysis was greater than the production of enzymes from the original Solka Floc.
Kinetic models for enzymic cellulose degradation in aqueous two‐phase systems
Authors: Mandenius Carl Fredrik , Nilsson Bernt , Persson Ingrid , Tjerneld Folke 
Published: December 2004

AbstractCellulose materials can readily be degraded into cellobiose and glucose by hydrolysis of the enzymes cellulase and β‐glucosidase in aqueous media. Product inhibition does, however, retard the reaction rate and reduce productivity. This may be avoided by carrying out the degradation of cellulose in an aqueous two‐phase system, which permits the enzymes and the substrate to be partitioned to one phase and the products to be extracted into a second phase. In addition, two‐phase systems also allow recycling of the enzymes. Here, three models previously developed for “one‐phase” enzymic degradation are compared to data from enzymic degradation in an aqueous two‐phase system. The models tested agreed relatively well with batch experiments during a period of 200 h. For one of the models tested, continuous degradation also gave accurate agreement.
Shear breakage of nylon membrane microcapsules in a turbine reactor
Authors: Poncelet Denis , Neufeld Ronald J. 
Published: December 2004

AbstractThe breakage of nylon membrane microcapsules is proposed as a new method to study and quantify shear effects in biological systems. A critique of this method shows that a narrower particle size distribution may be an important improvement in the breakage study as well as breakage control in many bioreactor and biotechnological applications. In a turbine reactor, it was shown that the primary process which determines the microcapsule breakage is the shear effect. The breakage kinetics are first order with regard to the microcapsule concentration. The breakage kinetic constant was ob served to be dependent on the temperature and the particle size, and proportional to the average shear rate and the third power of the turbine angular velocity. Decrease of the breakage kinetic constant with temperature can be explained by a decrease of fluid viscosity and a change in nylon membrane properties. An increase in the breakage kinetic constant with the microcapsule diameter can be due to a lowering of internal pressure and a reduction of the membrane resistance with size. Proportionality between the breakage kinetic constant and the shear rate shows that shear is the main process which leads to microcapsule breakage. The additional intervention in the shear rate expression of the turbine angular speed in the form of the turbine and particle velocities, results in the dependence of the breakage kinetic constant on the third power of the angular velocity.
A dispersion model for predicting the extent of starch liquefaction by Bacillus licheniformis α‐amylase during reactive extrusion
Authors: Komolprasert Vanee , Ofoli Robert Y. 
Published: December 2004

AbstractA Baker–Perkins corotating twin screw extruder was used as a bioreactor to hydrolyze pregelantinized corn starch by themophilic Bacillus licheniformis α‐amylase. The extruder was modeled as a tube, and characterized as a closed system. This characterization is not in the thermodynamic sense; rather, it relates to the profile of a tracer fluid upon entry to and exit from the reaction zone. The reaction kinetics were modeled by a modified first‐order equation, which allowed the dispersion equation to be solved analytically with the Danckwerts boundary condition. Data from several extrusion runs were super‐imposed to obtain a profile to evaluate the model. The dispersion number, determined from the first and second moments of the RTD curve, was primarily a function of the length of the reaction zone. There was good agreement between predictions and experimental data, especially at low dispersion numbers. In general, the axial dispersion model appears to be suitable for analysis of enzymatic reactions of up to 30% conversion. At a fixed flow rate and constant temperature, the extent of starch conversion depends significantly on moisture content, residence time and enzyme dosage, but not on screw speed.
Lipase‐catalyzed hydrolysis of 2‐naphtyl esters in biphasic system
Authors: Miyake Yoshikazu , Ohkubo Misahiro , Teramoto Masaaki 
Published: December 2004

AbstractThe authors measured the rate of hydrolysis of the homologs of 2‐naphtyl ester by using a Lewis cell with constant interfacial area to elucidate the kinetic mechanism of the lipase‐catalyzed hydrolysis in biphasic system. On the basis of the two‐film model, it was found from the analysis of experimental results that the hydrolysis of these substrates proceeds at the interface between the aqueous and organic phases. The interfacial reaction rate could be correlated by Michaelis–Menten mechanism. The values of the rate constant and the Michaelis constant were almost independent of the kinds of 2‐naphtyl ester. The values of the interfacial kinetic parameters for 2‐naphtyl ester were much greater than those for the hydrolysis in the aqueous phase.
Activity studies of eight purified cellulases: Specificity, synergism, and binding domain effects
Authors: Irwin Diana C. , Spezio Michael , Walker Larry P. , Wilson David B. 
Published: December 2004

AbstractThe activities of six purified Thermomonospora fusca cellulases and Trichoderma reesei CBHI and CBHII were determined on filter paper, swollen cellulose, and CMC. A simple method to measure the soluble and insoluble reducing sugar products from the hydrolysis of filter paper was found to effectively distinguish between exocellulases and endocellulases. Endocellulases produced 34% to 50% insoluble reducing sugar and exocellulases produced less than 8% insoluble reducing sugar. The ability of a wide variety of mixtures of these cellulases to digest 5.2% of a filter paper disc in 16 h was measured quantitatively. The specific activities of the mixtures varied from 0.41 to 16.31 μmol cellobiose per minute per micromole enzyme. The degree of synergism ranged from 0.4 to 7.8. T. reesei CBHII and T. fusca E3 were found to be functionally equivalent in mixtures. The catalytic domains (cd) of T. fusca endocellulases E2 and E5 were purified and found to retain 93% and 100% of their CMC activity, respectively, but neither cd protein could digest filter paper to 5.2%. When E2cd and E5cd were substituted in synergistic mixtures for the native proteins, the mixtures containing E2cd retained 60%, and those containing E5cd retained 94% of the original activity. Addition of a β‐glucosidase was found to double the activity of the best synergistic mixture. Addition of CBHI to T. fusca crude cellulase increased its activity on filter paper 1.7‐fold. © 1993 John Wiley & Sons, Inc.
Modulation of secretion of vasoactive materials from human and bovine endothelial cells by cyclic strain
Authors: Carosi Joseph A. , McIntire Larry V. , Eskin Suzanne G. 
Published: December 2004

AbstractThe effects of cyclical expansion and elaxation of the vessel wall on endothelial cell metabolism have been modeled using a uniaxial strain device and cultured endothelial cell monolayers. Also, the effects of stopping and then restarting cyclic strain on metabolite secreation rates were determined. Secretion rates of prostacyclin (PGI2), endothelin, tissue plasminogen activator (t‐PA), and plasminogen activator inhibitor‐type 1 (PaI‐1) by endothelial cells were constant over24‐h periods The secreation of both PGI2 and endothelin was enhanced in cells exposed to high physiological levels of cyclical strain (10% at 1Hz) compared with controls, while tPA production was unaltered. These results were true for both human and bovine endothelial cells. Characterization of the response of human endothelial cells to cyclical strain made evaluation of stretch effects on PAl‐1 secretion possible. A nearly twofold increase in PAl‐1 secretion by cells exposed to arterial levels of strain was observed. Endothelin secretion remained elevated even after strain was stopped for 12 h, while PGl2 secretion returned to control values upon cessation of cyclic stretch. These results indicate that physiological levels of cyclic mechanical strain ca significantly modulate secretion of vasoactive metabolited form endothelial cells. The changes sen secretion are, in some cases, quite different from those caused by arterial levels of fluid shear stress exposure. © 1994 John Wiley & Sons, Inc.
Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor
Authors: Xavier A. M. R. B. , Gonçalves L. M. D. , Moreira J. L. , Carrondo M. J. T. 
Published: December 2004

AbstractLactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long‐term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start‐up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h−1, D = 0.40 h−1, or D = 0.58 h−1). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h−1 being the one providing the best overall performance. On the other hand, results show that of the two start‐up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at “steady state,” the membrane permeability being kept around 15 L/m2 h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. © 1995 John Wiley & Sons, Inc.
Ion exchange of amino acids at a natural organic ion exchanger: Thermodynamics and energetics
Authors: Bowen W. Richard , Moran Enda B. 
Published: December 2004

AbstractThe thermodynamics and energetics of the ion exchange of four amino acids at a cellulosic ion exchanger have been studied. Experimental work included determination of ion exchange isotherms and the use of high‐sensitivity titration microcalorimetry. A rigorous thermodynamic analysis of the data was developed allowing calculation of the standard free energy, the standard enthalpy, and standard entropy of exchange, and also the differential free energy, incremental enthalpy, and incremental entropy of exchange. The results show that the relative contributions of the enthalpy and entropy to the overall free energy differ markedly for the chosen amino acids. The reasons for these differences are analyzed and discussed. A knowledge of these fundamental thermodynamic properties indicates the solution conditions likely to give enhanced affinity of the ion exchanger for selected amino acids. The experimental techniques and analysis procedures developed are generally applicable to ion exchange separations of biomolecules. © 1995 John Wiley & Sons, Inc.
Studies on the nervus terminalis: Mammals
Authors: Larsell Olof 
Published: January 2005

AbstractThe nervus terminalis of mammals is made up in part, at least, of sympathetic fibers, and its ganglionic clusters contain sympathetic cells. The wide distribution and large number of fibers of the peripheral plexus (as noted by Brookover), in comparison with the small size of the central connections, resemble the relation of preganglionic fibers to the postganglionic fibers of the sympathetic system. This resemblance is strengthened by the occurrence of pericellular baskets on inany of the ganglion cells of the intracranial clusters.
The anterior ventral cochlear nucleus
Authors: Harrison J. M. , Irving R. 
Published: January 2005

AbstractThe anterior cochlear nucleus was examined with a view to describing its subdivisions. The brains of 29 adult rats were paraffin embedded, sliced at 16 μ and impregnated according to the protargol method of Bodian. From examination of this material the nucleus was divided into three major regions.Region III contained round cells with short dendrites which received as synaptic endings two or three bulbs of Held and many terminal rings. The cells of the region gave rise to small diameter (less than 1 μ) nerve fibers which entered the trapezoid body. This region appeared to be identical with region III of Lorente de No.Region II occupied the ventral one third of the nucleus and contained cells of various types, Synaptic endings in this region consisted principally of terminal rings of various sizes and complexities. Nerve fibers which originated in this region were between 1.0 μ and 2.2 μ in diameter and entered the trapezoid body. The region did not conform to region II of Lorente de No.Region I occupied the dorsal two thirds of the nucleus and contained medium and small cells. Synaptic endings consisted of pale, small bulbs of Held. This region differed from region I of Lorente de No.
Selectivity in fasciculation of nerve fibers in Vitro
Authors: Nakajima Shinshu 
Published: January 2005

AbstractInteractions between nerve fibers were observed in the dissociated cultures of spinal ganglion cells from chick embryos. After a nerve fiber made filopodial contacts with another fiber, three types of interactions were found: the two fibers formed a bundle, one crossed over the other, or one or both fibers retracted. It is suggested that selectivity among nerve fibers with regard to fasciculation is exerted through the filopodial contacts.
Redefinition of the macula neglecta in mammals
Authors: Igarashi Makoto 
Published: January 2005

AbstractThe rudimentary sensory end organ in the vestibule at the junctions of the utricle and semicircular canals was investigated in 70 mammalian inner ears, cut serially in horizontal plane. The epithelial mound at the horizontal semicircular canal‐utricular junction, which has been called macula neglecta, was observed in almost all of the human and dog specimens and in 25% of the squirrel monkeys. The designation “epithelial moud of latero‐posterior utricular fold” is recommended. In the cat and dog, but in none of the other mammalian ears examined, a rudimentary sensory end organ was observed on the anterior medial wall of the inferior utricular sinus. The designation “sensura neglecta” is suggested.
Perinatal changes in epidermal innervation in rat and mouse
Authors: Fitzgerald M. J. T. 
Published: January 2005

AbstractThe development of cutaneous innervation in the rat and the rat and the mouse has been studied by silver techniques. In particular, the innervation patterns of adult and of perinatal skin have been compared. From the second parental day until the sixth postnatal day, the relatively thick epidermis is freely penetrated by nerve fibers; thereafter, the nerve endings appear to be confined to the dermis. The intra‐epidermal axons are directed obliquely, with a rough (and not exact) correspondence to the plane of future emergence of the hair shafts. The appearance of a transitory development of intra‐epidermal nerves elsewhere.
A peculiar mode of muscular innervation in amphioxus. Light and electron microscopic studies of the so‐called ventral roots
Authors: Flood Per R. 
Published: January 2005

AbstractThe present study demonstrates a neuromuscular junction between the so‐called ventral root fibers and the surface of the spinal cord of amphioxus.The ventral root fibers, interconnected by numerous zonulae occludentes, appear to be projections from muscle fibers of the myotome and end in conical expansions at the surface of the spinal cord, separated from an extensive layer of axon endings or boutons by an extracellular cleft containing a basement membrane.Within each ventral root two kinds of ventral root fibers can be identified. Each corresponds to a compartment of the bouton layer. The so‐called thick ventral root fibers are opposed to a long ventral compartment of small boutons tightly packed with vesicles about 1,000 Ä in diameter, but without a dense core. The so‐called thin ventral root fibers are opposed to a short dorsal compartment of large boutons filled with synaptic vesicles about 600 Ä in diameter.