bluuebunny/crossref_metadata_2025 huggingface dataset:
A formulation for correlating properties of peptides and its application to predicting human immunodeficiency virus protease‐cleavable sites in proteins
Authors: Chou James J.
Published: December 2004

A mathematical frame has been established to generally formulate the correlating properties of peptides. The formulation can be used to study the specificity of multisite enzymes, particularly in predicting the susceptible sites in proteins by human immunodeficiency virus (HIV) proteases, and hence can serve as a supplementary means in designing HIV protease inhibitors as potential drugs against acquired immunodeficiency syndrome. © 1993 John Wiley & Sons, Inc.
Effect of various frictional models on long‐time peptide dynamics
Authors: Kostov Konstantin , Freed Karl F. , Perico Angelo
Published: December 2004

We analyze the implications of various choices for atomic friction coefficients on a recent theory of long‐time peptide dynamics. One method for determining atomic friction coefficients is based on calculating effective hydrodynamic radii from the reduction of the atomic surface area accessible to solvent, while another employs an additive van der Waals radii model. These friction coefficients are used to evaluate the orientational correlation times of bonds in the peptide fragment ACTH(5–10), which contains a single tryptophan probe. Three models are considered; they choose as relevant slow variables (a) the positions of the α‐carbons, (b) the positions of all backbone bonds, and (c) both positions in (b) and those along side chains. Comparisons are made between the three models and with experiment. While general variations are similar, large shifts in local correlation times emerge from using the different methods. The results indicate that the extra backbone bonds do not contribute much to the memory function for the virtual bond model, but the side‐chain groups have a strong effect. © 1993 John Wiley & Sons, Inc.
Simulation of α‐helix–coil transitions in simplified polyvaline: Equilibrium properties and brownian dynamics
Authors: Schneller William , Weaver David L.
Published: December 2004

A quantitative understanding of helix–coil dynamics will help explain their role in protein folding and in folded proteins. As a contribution to the understanding, the equilibrium and dynamical aspects of the helix–coil transition in polyvaline have been studied by computer simulation using a simplified model of the polypeptide chain. Each amino acid residue is treated as a single quasiparticle in an effective potential that approximates the potential of mean force in solution. The equilibrium properties examined include the helix–coil transition and its dependence on chain position and well depth at the coil–helix interface. A stochastic simulation of the Brownian motion of the chain in its solvent surroundings has been used to investigate dynamical properties. Time histories of the dihedral angles have been used to study the behavior of the helical structure. Auto and cross‐correlation functions have been calculated from the time histories and from the state (helix or coil) functions of the residues with relaxation times of tens to hundreds of picoseconds. Helix–coil rate constants of tens of ns−1 were found for both directions of the transition. © 1993 John Wiley & Sons, Inc.
Molecular dynamics analysis of a ribonuclease C‐peptide analogue
Authors: Soman Kizhake V. , Karimi Afshin , Case David A.
Published: December 2004

We have carried out a nanosecond molecular dynamics simulation of an analogue of the ribonuclease C‐peptide in water. The overall conformation has an extended region for the first three amino acids connected to an α‐helix for residues 4–13, and this basic structure is preserved throughout the simulation, with helical hydrogen bonds present 87% of the time, on average. The final helical hydrogen bond is spontaneously broken and re‐formed several times, providing a detailed picture of such winding/unwinding events. The simulation was used to estimate the effects of internal motion on proton nuclear Overhauser effect spectroscopy (NOESY) intensities for several classes of important cross peaks. Within the helical regions, the effects of internal motion vary only a little from one residue to another for backbone–backbone cross peaks, and the relevant correlation functions reach plateau values within about 50 ps. The spectral simulations show, however, that it may be difficult to establish a close quantitative connection between NOESY cross‐peak volumes and measures of helical content. © 1993 John Wiley & Sons, Inc.
Assessment of protein rotational diffusion by 13C off‐resonance rotating frame spin–lattice relaxation: Effect of backbone and side‐chain internal motion
Authors: Wang Sharon X. , Stevens Arthur , Schleich Thomas
Published: December 2004

The 13C off‐resonance rotating frame spin–lattice relaxation technique is applicable to the study of protein rotational diffusion behavior in a variety of experimental situations. The original formalism of James and co‐workers (1978) (J. Am. Chem. Soc. Vol. 100, pp. 3590–3594) incorporated random isotropic reorientational motion of a rigid spherical rotor with no provision for backbone or side‐chain carbonyl group internal motion. Here we demonstrate that the failure to include such internal motion may lead to erroneous rotational correlation time determinations for overall reorientational motion. The effect becomes severe for protein molecular masses in excess of 100 kD. Inclusion of both backbone and side‐chain carbonyl carbon internal motion, using reasonable parameters derived from the literature [R. Levy and M. Karplus (1979), Chemical Physics Letters, Vol. 65, pp. 4–11; G. Careri, P. Fasella, and E. Gratton (1975), Critical Reviews in Biochemistry, Vol. 3, pp. 141–164; G. Lipari, A. Szabo, and R. Levy (1982), Nature, Vol. 300, pp. 197–198], plus corrections for anisotropic tumbling [C. F. Morgan, T. Schleich, G. H. Caines, and D. Michael (1990), Biopolymers, Vol. 29, pp. 469–480] and microscopic viscosity [S. H. Koenig (1980), ACS Symposium. Series, Vol. 127, pp. 157–176], leads to reliable values for the correlation time describing overall protein reorientation up to molecular masses of approximately 1000 kD. © 1993 John Wiley & Sons, Inc.
Comparative study of the interactions of cisplatin and carboplatin with nucleotides using UV resonance raman spectroscopy
Authors: Benson Ronda L. , Gustafson Terry L.
Published: December 2004

We have obtained the UV excited resonance Raman spectra of five mononucleotides bound to cisplatin and to carboplatin using excitation in resonance with the first electronic absorption bands of the nucleotide bases. Substantial changes in the spectra are observed following interaction with both platinum drugs, indicating modifications to nucleotide structure. Pt (II) binds to base portions of the nucleotide molecules, altering their normal modes of vibration significantly. We present comparative data of cisplatin and carboplatin, and discuss the implications of these results. The kinetics of the drug/nucleotide reactions differ, but final products are found to be similar. © 1993 John Wiley & Sons, Inc.
Conformation and interactions of bombolitin I analogues with SDS micelles and phospholipid vesicles: CD, fluorescence, two‐dimensional NMR and computer simulations
Authors: Chorev Michael , Gurrath Marion , Behar Vered , Mammi Stefano , Tonello Antonella , Peggion Evaristo
Published: December 2004

Bombolitins are five structurally related heptadecapeptides acting at the membrane level able to lyse erythrocytes and liposomes and to enhance the activity of phospholipase A 2(PLA2). In the presence of SDS or phospholipid vesicles bombolitins are able to form amphiphilic α‐helical structures and this property seems to be the major determinant of bioactivity. In order to test the model of interaction between bombolitin I and membranes, an analogue was synthesized in which all the lysines were replaced by arginines:

([Arg2,9,12, Ile10] bornbolitin I). The design ofthis sequence allowed the synthesis of a second analogue through a specijic postsynthetic dansylation at the ϵ‐amino group qf a lysine residue replacing the original leucine residue at position 7. The, first analogue was, fiilly characterized by CD and two‐dimensional nmr in the presence of SDS or phospholipid vesicles. The peptide, folds into an amphiphilic α‐helical confbrrnation with the helical segment spanning the central part of the sequencefrom Ile3 to His16. This behavior is identical to that observed for the native sequence. The replacement of Iysine residues by arginine hus no detectable effect on the conformational prderence of the peptide chain. By CD and fluorescence spectroscopy measurements, the fluorophore‐containing analogue [Arg2,9,12, Lys7(ϵ‐dansyl)] bombolitin I also folded into the α‐helical conformation in the presence of SDS micelles or phospholipid vesicles. In particular, the dansyl fluorophore, which is located approximately in the middle of the apolar surface ojthe amphiphilic helix, is clearly buried in a hydrophobic environment when the peptide is bound to phospholipid vesicles. These findings support the hypothesis that the peptide helices are oriented parallel to the vesicle surface. © 1995 John Wiley & Sons, Inc.
Conformation of parathyroid hormone antagonists by CD, nmr, and molecular dynamics simulations
Authors: Chorev Michael , Behar Vered , Yang Quming , Rosenblatt Michael , Mammi Stefano , Maretto Stafano , Pellegrini Maria , Peggion Evaristo
Published: December 2004

The conformation of two highly potent parathyroid hormone (PTH) antagonists was investigated in water/2, 2, 2‐trifluoroethanol mixtures. The two peptides are derived from the sequence (7‐34) of PTH and of PTH‐related protein (PTHrP) and have a D‐Trp replacing Gly in position 12. In the analogue derived from PTHrP, Lys11 was replaced by Leu to remove the residual agonist activity. The study was conducted by CD and two‐dimensional proton magnetic resonance spectroscopy, and the nuclear Overhauser effects found were utilized in restrained distance geometry and molecular dynamics simulations.

Both peptides adopt a helical C‐terminal conformation, which seems more stable in the case of the PTHrP analogue. A type II′ β‐turn centered around D‐Trp12 and Lys13 is present inboth structures. © 1995 John Wiley & Sons, Inc.
Conformational analysis of dolastatin 10: An nmr and theoretical approach
Authors: Benedetti E. , Carlomagno T. , Fraternali F. , Hamada Y. , Hayashi K. , Paolillo L. , Shioiri T.
Published: December 2004

A solution conformational analysis of dolastatin 10, a powerful antineoplaslic agent, has been carried out by means of nmr techniques and theoretical calculations. 1H mono‐ and bidimensional nmr experiments, as well as 1H‐13C heterocorrelated spectra, have been performed on CD2Cl12 solutions. The most interesting nmr data is a huge shielding of the aCH (25) proton of the Dov residue, suggesting the presence of an interaction between the N‐terminal and the aromatic C‐terminal ends of the molecule.

The possibility of a head‐to‐tail intermolecular association having been discarded, the presence of a series of preferred folded conformation has been hypothesized. Conformational theoretical analysis supports the nmr hypothesis of a folded peptide‐like molecule, and a series of possible conformers in good agreement with the experimental data have been analyzed. © 1995 John Wiley & Sons, Inc.
Microbial production of amino acids. II. The influence of carbon and nitrogen sources and metal ions on growth of Ustilago maydis (DC.) Cda. and on lysine and threonine production
Authors: Kurz W. G. , Ericson L.‐E.
Published: December 2004

The ability of Ustilago maydis (DC.) Cda. to grow and to produce lysine and threonine was investigated in shake flask cultures. Growth and production of lysine and threonine increased markedly when aeration was increased. The optimal ratio of glucose to diammonium phosphate in the medium seemed to be approximately 10:1. Ammonium phosphate, ammonium sulfate, ammonium chloride, ammonium nitrate, sodium nitrate, urea, aspartic acid, glutamic acid, and glycine were readily used as nitrogen sources. Growth and amino acid production was poor on ammonium carbonate, ammonium acetate, ammonium citrate, trimethylamine, and betaine.

U. maydis (DC.) Cda. was found to grow on a number of different carbohydrates. Besides D‐glucose the organism could utilize D‐mannose, D‐galactose, D‐fructose, L‐arabinose, D‐xylose, D‐ribose, sucrose, maltose, and the polyalcoholes D‐sorbitol, D‐mannitol, and i‐inositol. Pectin, dextrin, and corn starch treated with α‐amylase could also be used but not untreated corn starch or lactose, cellobiose, D‐sedoheptulose, glycerol, or D‐glucosamine. The formation of lysine and threonine was better with disaccharides and hexoses than with pentoses.

No specific effects on the formation of lysine and threonine could be observed from changes in the concentration of calcium, sodium, potassium, magnesium, zinc, iron, copper, manganese, cobalt, or molybdenum. The requirement of metal ions for growth is discussed.
Preparation and characterization of isolubilized L‐amino acid oxidase
Authors: Weetall H. H. , Baum G.
Published: December 2004

The enzyme L‐amino acid oxidase of Crotalus adamanteus was covalently coupled to porous 96% silica glass particles. The insolubilized enzyme was active on several L‐amino acids including: leucine, isoleucine, cysteine, phenylalanine, tryptophane, and methionine. No activity was observed with D‐amino acids, L‐asparagine, or L‐proline. Maximum activity was observed at pH 7.8. Stability of the enzyme derivative was demonstrated by continuous operation of an enzyme column for 35 days, during which the bound enzyme oxidized over 5000 times its own weight of substrate.
Design and evaluation of a system for thermal decontamination of process air
Authors: Chatigny M. A. , Sarshad A. A. , Pike G. F.
Published: December 2004

Aerobiology studies at the Naval Biological Laboratory require use of a vacuum system to provide safe disposal of air contaminated with pathogenic, microorganisms. A system for thermal decontamination of this process air has been installed and tested. The system uses a natural gas burner to heat approximately 550 cfm of air to temperatures exceeding 750°F. Tests showed a reduction in number of acrosolized viable hardy spores (Bacillus subtilis var. niger) of more than 8 logs at design flow rates. The kill rate (D values) measured in this system is somewhat higher than those reported by other workers. The annual owning and operating cost of the system is approximately $9000.
Application of ultrafiltration for enzyme. Retention during continuous enzymatic reaction
Authors: Butterworth T. A. , Wang D. I. C. , Sinskey A. J.
Published: December 2004

In most enzymatic reactions, batch or continuous, separation of the enzyme for reuse is difficult if not impossible. A process will be presented in which an Ultrafiltration membrane serves to separate the reaction products from the enzyme and the substrate. In this manner the enzyme may be retained and re‐used. Furthermore, under these conditions, the enzyme need only be present in catalytic amounts regardless of the amount of product produced.

Under proper operating conditions and proper ultrafiltration membrane selection, a pure solution of α‐amylase from Bacillus subtilis may be retained with no loss in enzyme activity over a test period of 30 hr after steadystate has been achieved. In the presence of substrate, the membrane support and ultrafiltration cell serve as the reaction vessel for the hydrolysis of starch. The substrate is continuously pumped into the cell under constant ultrafiltration pressure. The di‐, oligo‐, and polysaccharides formed from the enzyme reaction then either pass through the membrane as products or are retained. The molecular weight distribution of the products is dependent on the nominal molecular weight cut‐off of the membrane, absolute ultrafiltration pressure, enzyme‐to‐substrate ratio, temperature, and residence time of the substrate in the reactor. In addition to the partial hydrolysis of starch by α‐amylase, some preliminary findings on the complete hydrolysis of starch by glucoamylase will also be presented. In these latter studies, the substrate may be completely hydrolyzed to glucose units.
Degradation and mineralization of petroleum by two bacteria isolated from coastal waters
Authors: Atlas Ronald M. , Bartha Richard
Published: December 2004

Within the framework of a study on the oil biodegradation potential of the sea the ability of a Flavobacterium sp. and Brevibacterium sp. to metabolize a paraffinic crude oil and a chemically defined hydrocarbon mixture was investigated. Major components of the crude oil were identified by combination gas chromatography and mass spectrometry. The rate and extent of total hydrocarbon biodegradation was measured. In addition, CO2 evolution from the crude oil was continuously monitored in a shaker‐mounted gas train arrangement. Degradation started after a 2 to 4 day lag period, and reached its maximum within two weeks. At this time up to 60% of the crude oil and 75% of the model hydrocarbon mixture, each added at the level of 1 ml per 100 ml artificial sea water, were degraded. Mineralization(conversion to CO2) was slightly lower due to formation of products and bacterial cell material. n‐Paraffins were preferentially degraded as compared to branched chain hydrocarbons. Biodegradation of n‐paraffins in the range of C12 to C20 was simultaneous; no diauxie effects were observed.
Effects of growth rate and influent substrate concentration on effluent quality from chemostats containing bacteria in pure and mixed culture
Authors: Grady C. P. L. , Harlow L. J. , Riesing R. R.
Published: December 2004

Studies were performed using pure cultures of A. acrogenes and E. coli and a heterogeneous microbial population growing in carbon‐limited chemostats with glucose as the sole carbon and energy source. A two‐level factorial experimental design was employed to test the hypothesis that the concentration of growth‐limiting substrate in a chemostat is controlled by the growth rate alone and is independent of the concentration of substrate entering the reactor. The pure culture experiments showed that the conclusions depend upon the measurement employed for growth‐limiting substrate. When the concentration of glucose was measured directly, the hypothesis was found to be true within the limits of the study (500–1500 mg/liter). However, if the chemical oxygen demand (COD) test was used as the measure of growth‐limiting substrate the hypothesis was found to be false. When heterogeneous cultures were employed the hypothesis was false regardless of the technique used to measure the concentration of growth‐limiting substrate. Nevertheless, it was possible to generate regression equations which described the interactions among influent COD, growth rate, and effluent COD with a high level of correlation.
Growth models of cultures with two liquid phases. VIII. Experimental observations on droplet size and interfacial area
Authors: Prokop A. , Ludvik M. , Erickson L. E.
Published: December 2004

Because of the importance of the drop she distribution and interfacial area of the dispersed liquid phase in hydrocarbon fermentations, experiments were carried out to determine the drop size distribution and the interfacial area during batch fermentations ofCandida lipolyticaon gas oil and onn‐hexadecane dissolved in dewaxed gas oil. The effects of cell concentration and dispersed phase volume fraction on size distribution and interfacial area were investigated. Measurements of interfacial tensions, densities, viscosities, and fatty acid concentrations were also made. The results show that the size distribution is skewed and that the Sauter mean diameter is in the range of 10 to 30 μ. Both the Sauter mean diameter and the interfacial area increased during the course of a batch fermentation; however, they decreased at the end of the fermentation. The interfacial area also increased with inoculum size.
Invertase covalently coupled to porous glass: Preparation and characterization
Authors: Mason R. D. , Weetall H. H.
Published: December 2004

The enzyme invertase has been covalently coupled to porous glass particles. The product is extremely stable over a long period of time. Kinetic values for the immobilized enzyme are similar to the native enzyme. Excellent enzymatic activity for the immobilized enzyme was exhibited over a broad pH range. The immobilized enzyme when continuously operated for one month was found to have an operational half‐life of over 40 days.
Kinetic studies of C. pyrenoidosa using 94% 13C CO2
Authors: Fowler Eric B. , Adams W. H. , Christenson C. W. , Kollman V. H. , Buchholz J. R.
Published: December 2004

The alga Chlorella pyrenoidosa has been grown in mass quantities on 94 at. % 13CO2. The algal cells have been labeled to the 90 at. % 13C level. Neither inhibition nor a requirement for adaptation was encountered; changes in morphology were not evident. A statistically significant increase in mass of cells produced in the presence of 13CO2 was observed.
Collagen‐enzyme complex membranes and their performance in biocatalytic modules
Authors: Wang S. S. , Vieth W. R.
Published: December 2004

Collagen was used as carrier for the immobilization of invertase, lysozyme, urease, glucose oxidase, penicillin amidase, and glucose isomerase. Immobilization was accomplished by either impregnation of a preswollen collagen membrane with enzyme solution or electrocodeposition of collagen and enzyme from a collagen dispersion containing dissolved enzyme. The collagen‐enzyme complexes prepared are in membrane form.

Membranous collagen‐enzyme complexes were used to construct biocatalytic reactors such as the capillaric coil modular reactor. Such biocatalytic reactors were used in a recirculation system for the conversion of substrates. The biocatalytic reactors showed initial decreases of activity to stable limits which are maintained over a large number of reactor volume replacements. The stable limits correspond to approximately 35% of the initial activities for lysozyme and invertase, 25% for urease, 15% for glucose oxidase.

The mechanism of complex formation between collagen and enzyme involves multiple salt linkages, hydrogen bonds, and van der Waals interactions. This protein‐protein interaction which leads to stable complexes by both impregnation and electrocodeposition processes is unique among the enzyme immobilization methods currently available.
Effectiveness factor calculations for immobilized enzyme catalysts
Authors: Fink David J. , Na Tsungyen , Schultz Jerome S.
Published: December 2004

The steady state, nonlinear diffusion equations which describe reactions in constrained enzyme solutions are of great interest in many biological and engineering applications. As in other types of nonlinear differential equations, exact analytical solutions do not exist except in some simplified cases. In this paper, a general procedure is presented for solving numerically for the substrate concentration profile and effectiveness factor utilizing the transformation method suggested by Na and Na. Design correlations for enzyme solutions constrained within spherical membranes are included. The use of a unique definition of the Thiele Modulus in these charts permits the clear illustration of the effects of substrate concentration and external mass transfer resistances on the overall effectiveness factor for the catalyst particle.
Lysis ofMicrococcus lysodeikticus by lysozyme covalently immobilized on cellulose and polyacrylamide
Authors: Datta R. , Armiger W. , Ollis D. F.
Published: December 2004

Lysozyme immobilized on polyacrylamide beads or cellulose fibers is found to retain activity for hydrolysis of the cell walls of Micrococcus lysodeikticus. The immobilization on cellulose is somewhat reversible; the polyacrylamide immobilized lysozyme does not release any enzyme upon washing as evidenced by UV and lytic activity tests. The specific catalytic activity of the lysozyme‐polyacrylamide system is found to decline as the density of derivatized surface groups is increased; a model of protein deactivation due to excess surface coupling is presented as a possible rationale for such specific activity variations.
Starch conversion by soluble and immobilized α‐amylase
Authors: Linko Yu‐Yen , Saarinen P. , Linko M.
Published: December 2004

B. subtilis α‐amylase was immobilized on cyanogen bromide activated carboxymethyl cellulose. The conversion of wheat starchwas carried out at 72°C in a stirred tank by soluble and immobilized α‐amylase. The initial reaction rate with immobilized α‐amylase was lower than with the soluble enzyme, but after 1 hr immobilized α‐amylase produced a higher quantity of reducing sugars than the soluble enzyme. The action pattern of immobilized α‐amylase was different from that of the soluble enzyme: immobilized α‐amylase produced relatively more glucose and maltose, except at the beginning of conversion. Immobilized α‐ readily hydrolyze G6. The starch conversion by immobilized α‐amylase was not diffusion controlled at a stirring rate of 100‐300 rpm.
Shear modification of enzyme kinetics
Authors: Tirrell Matthew , Middleman Stanley
Published: December 2004

No Asbtract.
Lactase and other enzymes bound to chitin with glutaraldehyde
Authors: Stanley W. L. , Watters G. G. , Chan B. , Mercer J. M.
Published: December 2004

Acid tolerant lactase (I), α‐chymotrypsin (II), and acid phosphatase (III) were immobilized on chitin with glutaraldehyde. Pretreatments of the chit in with acid, alkali, ammonia, and pronase were compared with respect to release of titratable amino groups and ability to retain lactase activity. Shrimp chitin appeared to be more sensitive to pretreatment conditions and so effort was concentrated on crab. An acid‐alkali pretreatment was selected as most practical and economical, and the properties of enzymes fixed on crab chitin were studied intensively. The pH optima of the fixed enzymes were shifted about one pH unit; the shift for I was toward more acid pH, for II was toward alkaline pH, and for III was toward acid pH. The retained activity of immobilized I was approximately 60% that of the native enzyme. A column in continuous operation with I on chitin‐glutaraldehyde gave an apparent activity half‐life of 27 days.
The enzymatic transformation of water‐insoluble reactants in nonaqueous solvents. Conversion of cholesterol to cholest‐4‐ene‐3‐one by a Ncardia sp.
Authors: Buckland B. C. , Dunnill P. , Lilly M. D.
Published: December 2004

The rapid conversion of cholesterol to cholestenone by Nocardia in the presence of high proportions of water‐immiscible solvent has been demonstrated. At high agitator speeds, the reaction rate was not limited by the rates of transfer of oxygen or cholesterol to the microorganisms. Using 100 g of thawed cells in 200 ml of carbon tetrachloride containing 16% (w/v) cholesterol, at 20°C cholestenone was formed at 7 g/hr. Cells could be separated easily from the organic solvent and reused. After 7 runs (69 hr) the reaction rate had fallen only to half the value for the first run.
Continuous hydrolysis of sucrose by invertase adsorbed in a tubular reactor
Authors: Boudrant Joseph , Cheftel Claude
Published: December 2004

Studies were made of invertase adsorption on Amberlite ion exchange resins. Up to 4000 units of adsorbed enzymatic activity (aea) were obtainedper g of IRA 93 resin; for an aea of 1600 units, the maximum ratio of aea over units of soluble enzyme used for adsorption was close to 50%. Nodesorption occurred during extensive washing at 30°C with 0.01Msodiumacetate buffer at pH 5. Progressive desorption of aea from the invertase–IRA 93 complex occurred when buffer molarity and temperature were increased. Desorption differed only slightly when the buffer pH was 3 or 5. Theoptimum pH of aea was 3.2 with IRA 93 resin, and varied between 3.2 and 5.1with other resins, depending on their anionic or cationic nature. Batch hydrolysis of sucrose by IRA 93–adsorbed invertase followed 1st order kinetics with respect to the substrate concentration, as in the case of soluble invertase.

Continuous sucrose hydrolysis with IRA 93–adsorbed invertase was performed in a tubular reactor, and the percent conversion was experimentally determined as a function of the flow rate. The reaction was experimentally determined 50% (w/v) sucrose solution, at pH4 and 30°C; at the selected flow rate, the ratio of sucrose hydrolysis remained constant and close to 76%. This shows that invertase was not desorbed from the tubular reactor. Some continuous hydrolyses were performed with an industrial sucrose solution: enzymatic activity seemed to be stable for anextended period for time (1 month) at 30°C and pH 3 or 4.
Dynamics of mixed populations having complementary metabolism
Authors: Meyer James S. , Tsuchiya H. M. , Fredrickson A. G.
Published: December 2004

The dynamics of a system of two microbial populations having complementary metabolism are investigated by means of simple mathematical models of growth. Complementary metabolism as used here means that each population produces a substance—not present in the initial or feed medium—required by the other for growth. The simple models indicate that (1) something other than lack of the substrate or growth factor produced by its partner must limit the growth of at least one population and (2) the coexistence steady state of such populations in continuous culture is not stable with respect to large perturbations, though it is stable with respect to a wide range of perturbations.
Engineering analysis of continuous production of L‐aspartic acid by immobilized Escherichia coli cells in fixed beds
Authors: Sato Tadashi , Mori Takao , Tosa Tetsuya , Chibata Ichiro , Furui Masakatsu , Yamashita Kiyokazu , Sumi Akihiko
Published: December 2004

The reaction mechanism and decay behavior of aspartase activity for immobilized Escherichia coli cells were investigated by using a sectional packed column.

Reaction within the immobilized cell column proceeded at zero‐order on substrate solutions ranging in concentration from 0.1 to 1.0M, and the initial reaction rate was found to be 1.556 × 10−2 mol/min/liter of immobilized cells.

The effect of temperature on the reaction rate constant was investigated. The Arrhenius plot was straight line at temperatures below 43°C, and the activation energy for immobilized cells was calculated to be 12.36 kcal/mol.

Asparatase activity in the immobilized cell column decayed exponentially and uniformly in all sections of a column. Its half‐life was approximately 120 days.

The rate of formation of L‐aspartic acid was shown to be independent of column dimensions.
Enzyme mechanisms involved in cellulose hydrolysis by the rot fungus Sporotrichum pulverulentum
Authors: Eriksson Karl‐Erik
Published: December 2004

This article presents a review of the enzyme mechanisms involved in degradation of cellulose by the white‐rot fungus Sporotrichum poulverulentum. The hydrolytic enzymes involved include: (1) five endo‐1,4‐β‐glucanases; (2) one exo‐1,4‐β‐glucanase, and (3) one or several 1,4‐β‐glucosidases. A recently discovered oxidative enzyme of importance in in vitro cellulose degradation seems to be a cellobiose oxidase. An oxidoreductase, cellobiose:quinone oxidoreductase, is of importance both in cellulose and in lignin degradation. Regulatory mechanisms of the extracellular enzyme activities, such as monosugar levels causing catabolite repression of the endoglucanases, have also been investigated. The enzymes used by S. pulverulentum in cellulose hydrolysis are compared to those used by Trichoderma viride. Very similar types of enzymes are used in both cases. However, no oxidative enzyme has so far been found to be involved in extracellular cellulose degradation in the case of T. viride. Recommendations for further research are given.
Fungal cellulases as an aid for the saccharification of cassava
Authors: De Menezes Tobias J. B. , Arakaki Tomas , DeLamo Paulo R. , Sales Arlindo M.
Published: December 2004

Culture broths of cellulolytic fungi were used together with commercial amylases to enhance the saccharification of cassava starch slurry. It was found that the addition of appropriate concentration of the cellulases Trichoderma viride and a soil isolated Basidiomycete, increased both the rate of sugar formation and the degree of solubilization, and decreased the viscosity of the hydrolyzates. Owing to the improvement of the rheological properties of the must, and the additional sugar produced, an increased ethanol yield would be expected from the alcoholic fermentation of this hydrolyzate.
Effect of thiol reagents on extractability of protein from yeast
Authors: Shetty K. Jayarama , Kinsella John E.
Published: December 2004

The effect of soluble thiol reagents on the extractability of protein from yeast cells was studied. The incubation of yeast cells with dithiothreitol, 2‐mercaptoethanol, or monothioglycerol markedly stimulated the release of soluble carbohydrates into the medium. There was a concomitant improvement (over twofold) in the extractability of protein from the yeast cells. The thiol reagents activated the proteolytic enzymes of the yeast cells. Unless inactivated, these enzymes hydrolyze the extracted protein.
Stabilization of proteolytic enzymes in solution
Authors: Feder Joseph , Kochavi Daniel , Anderson Richard G. , Wildi Bernard S.
Published: December 2004

The stability of the neutral and alkaline proteases in a Bacillus subtilis enzyme mixture was studied in aqueous solutions at room temperature. Stabilization of the proteases in solution for periods up to 25 days was achieved by the addition of various protein preparations including casein and soya protein. The degree of stabilization by casein was concentration dependent to about 2% protein. The instability of the neutral protease in solutions of the B. subtilis enzyme mixture was shown to be due primarily to proteolysis by the alkaline protease since the diisopropylfluorophosphate‐treated enzyme was quite stable. Formulation of such enzyme solutions at low pH gave greater stability as did solutions containing an alkaline protease inhibitor from potatoes. A Conceptual approach to the formulation of enzyme solutions containing proteolytic enzyme to ensure maximum stability is proposed.
Influence of manufacturing variables on the characteristics and effectiveness of chitosan products. II. Coagulation of activated sludge suspensions
Authors: Bough W. A. , Wu A. C. M. , Campbell T. E. , H0Lmes M. R. , Perkins B. E.
Published: December 2004

Chitosan samples manufactured under different conditions were compared for effectiveness of coagulating an activated sludge suspension grown on vegetable canning wastes. Computer analysis of data from Buchner funnel filterability tests resulted in quadratic polynomial equations describing the response curves for volume of filtrate versus dosage, expressed as g/liter chitosan/100 g sludge suspended solids (SSS). The quotient of the filtrate volume and dosage at the inflection points of the equations obtained for 10 test samples and 1 commercial chitosan sample were compared to evaluate the response (effectiveness) per unit amount for each chitosan product. The product made by a standard procedure (deproteinated with 3% NaOH at 100°C for 1 hr, demineralized with 1N HCL at ambient temperature for 30 min, and deacetylated with 50% NaOH at 145–150°C under N2 for 5 or 15 min) gave the best performance as a coagulating agent for this activated sludge system. Other products, including the commercial preparation, required higher dosages to achieve the same effectiveness. Products deacetylated in the presence of sir rather than nitrogen decreased waste treatment effectiveness, which approximated the trends of reduced viscosity and molecular‐weight distribution. The products containing minerals were less effective than products from which minerals had been removed prior to deacetylation, but they were more effective than the enzyme treated sample and the commercial product. In general, although chitosan products obtained after 15 min deacetylation were more effective than those receiving 5 min deacetylation, effectiveness did not correlate linearly with viscosity and molecular‐weight distribution trends. However, chitosan products deacetylated for 15 min did show that the higher‐molecular‐weight products (0.65–1.1 × 106) were more effective coagulating agents for activated sludge than the manufactured product having the lowest molecular weight (0.47 × 106) and the commercial reference sample (0.56 × 106). Thus, higher values for molecular weight were predictive of greater effectiveness for coagulation of activated sludge suspensions.
Fluidized‐bed immobilized‐enzyme reactor for the hydrolysis of cornstarch to glucose
Authors: Allen B. R. , Charles M. , Coughlin R. W.
Published: December 2004

We have developed an economical fluidized‐bed immobilized‐enzyme cornstarch hydrolysis reactor employing an inexpensive glucoamylase‐on‐alumina (covalently bonded) catalyst having a high initial activity (130 units/g) and excellent long term stability (t1/2 = 6450 hr at 50°C). The reactor can give higher yields of dextrose from streams containing ∼30% (wt) low dextrose equivalent (DE) cornstarch than can a comparable fixed‐bed reactor because its design exploits the fact that fluidixation permits the use of very small catalyst particles (down to 50μm in our case) which overcomes the yield‐limiting diffusion‐associated problems encountered in the use of conventional fixed‐bed cornstarch hydrolysis reactors. Furthermore, even when small catalyst particles are used the fluidized‐bed reactor does not suffer from plugging and high pressure drop problems typical of fixed‐bed reactors. The results of an initial economic analysis based on bench‐scale results indicate that the processing cost for a plant using this new technology to produce 100 × 106lb dextrose/year from low DE cornstarch would be as much as 33% lower than for a comparable plant employing conventional soluble‐enzyme technology.
Optimization of growth surface parameters in microcarrier cell culture
Authors: Levine David W. , Wang Daniel I. C. , Thilly William G.
Published: December 2004

The microcarrier technique for the growth of anchorage‐dependent animal cells has been studied and significantly improved. Excellent cell growth (up to 5 × 106 cells/ml) has been obtained on a newly synthesized microcarrier optimized with respect to substitution with a positively charged exchange moiety. Various parameters of microcarrier culture were examined in order to identify the source of reported “toxicities” associated with this technique. The hypothesis that bead adsorption of nutrients is responsible for such “toxicities” was found to be inconsistent with our results, which suggest that microenvironmental effects are critical for cell propagation on microcarriers.
Correlation between X‐ray diffraction measurements of cellulose crystalline structure and the susceptibility to microbial cellulase
Authors: Sasaki Takashi , Tanaka Takashi , Nanbu Noriko , Sato Yohko , Kainuma Keiji
Published: December 2004

Chemical and physical treatments of cotton cellulose have been studied in order to elucidate the relationship between the degree of crystallinity of cellulose and the susceptibility of cellulose to cellulase. Cotton cellulose powder was treated with the following solvents: 60% H2SO4, Cadoxen, and DMSO‐p ‐formaldehyde. The dissolved celluloses were recovered at high yield of over 97% by addition of nine volumes of cold acetone. X‐ray diffraction for measurements of relative crystallinity showed that the crystalline structure of cellulose declined in quantity and perfection by the dissolving treatment and changed to an amorphous form that is highly susceptible to enzymatic hydrolysis. These reprecipitated celluloses were hydrolyzed almost completely within 48 hr by Aspergillus niger cellulase containing mainly 1,4‐β‐glucan glucanohydrolase (EC 3.2.1.4), without action of 1,4‐β‐glucan cellobiohydrolase (EC 3.2.1. 91). On the other hand, cryo‐milled cellulose (below 250 mesh) still had a crystalline structure, was resistant to cellulase, and gave a low percentage of saccharification. These results indicate that in pure cellulose there are good correlations between x‐ray diffractograms and susceptibility to microbial cellulase.
Growth and composition of Escherichia coli subjected to square‐wave perturbations in nutrient supply: Effect of varying frequencies
Authors: Pickett A. M. , Bazin M. J. , Topiwala H. H.
Published: December 2004

The effect of regularly varying the input nutrient concentration on the growth and composition (elemental and macromolecular) of Escherichia coli ML30 grown in chemostat culture is reported. After each change in substrate concentration a lag between the stimulus and organism response occurred, the magnitude of which was dependent upon the frequency of the perturbations. Both the growth yield and macromolecular composition of the cells were found to vary with the frequency of nutrient cycling: the yield decreased by some 10% as the cycle‐times decreased from 6.0 to 0.25 hr. It is suggested that maintaining microorganisms under controlled transient conditions might be useful in increasing yields of specific microbial products (e.g., single‐cell protein).
Multilayer immobilized‐enzyme filter reactors: Urease bound to nylon fabric filters
Authors: Shemer Lev , Granot Roni , Freeman Amihay , Sokolovsky Mordechai , Goldstein Leon
Published: December 2004

Urease was bound to commercially available nonwoven nylon fabric filters. Multilyer immoibilized‐enzyme filter reactors were constructed by packing varying numbers of urease‐nylon filters in a column. Owing to the relatively open structure and high mechanical strength of the filter fabric, compaction and pressure drop effects were minimal. The reactors could be operated in a wide range of substrate concentrations and flow rates under conditions where mass‐transfer limitations could be neglected. The kinetic behavior of the immobilized‐enzyme filter reactors could be described by a linear form of the integrated Michaelis‐Menten equation using a model based on the sequential action of the enzyme filters.
Immobilization of enzymes and microbial cells using carrageenan as matrix
Authors: Tosa Tetsuya , Sato Tadashi , Mori Takao , Yamamoto Kazo , Takata Isao , Nishida Yutaka , Chibata Ichiro
Published: December 2004

Conditions for the gelation of k ‐carrageenan, which is a new polymer for immobilization of enzymes and microbial cells, were investigated in detail. k ‐Carrageenan was easily induced to gel by contact with metal ions, amines, amino acid derivatives, and water‐miscible organic solvents. By using this property of k ‐carrageenan, the immobilization of enzymes and microbial cells was investigated. Several kinds of enzymes and microbial cells were easily immobilized with high enzyme activities. Immobilized preparations were easily tailor‐made to various shapes such as cube, bead, and membrane. The obtained immobilized preparations were stable, and columns packed with them were used for continuous enzyme reaction for a long period. Their operational stabilities were enhanced by hardening with glutaraldehyde and hexamethylenediamine.
Action of shear on enzymes: Studies with alcohol dehydrogenase
Authors: Thomas C. R. , Nienow A. W. , Dunnill P.
Published: December 2004

Yeast alcohol dehydrogenase (ADH) solutions (approximately 1 mg/ml, pH 7) were sheared in a coaxial cylindrical viscometer. This was fitted with a lid sealing the contents from the atmosphere and preventing evaporation. At 30°C after a total of 5 hr intermittent shearing at 683 sec−1 no losses of activity were observed. No losses were found after 5 hr continuous shearing and in a no‐shear control. At 40°C and 683 sec−1 there were only small activity losses in 5 hr. Shearing at 3440 sec−1 no measurable losses of activity were found with a 1.03 mg/ml solution in 5 hr at 30°C, a 1.03 mg/ml solution in 8 hr at 5°C, and with a 3.89 mg/ml solution in 3 hr at 5°C. In all these cases, however, a white precipitate formed that was not observed in zero shear control experiments. The sheared 3.89 mg/ml solution was clarified by centrifugation. It was shown that there were no ADH aggregates in the supernatant and that the precipitate was less than 2% of the original protein. At 30°C under adverse pH conditions (pH 8.8) there was no significant difference in activity losses of an approximately 1 mg/ml solution sheared at 65 and 744 sec−1. An approximately 0.5 mg/ml ADH solution, pH 7, was agitated in a small reactor with no free air–liquid interface. Peak shear rates near the impeller were estimated to be about 9000 sec−1. Only a small decrease in specific activity was observed until over 15 hr total running at 5°C.
Factors influencing fungal degradation of lignin in a representative lignocellulosic, thermomechanical pulp
Authors: Yang H. H. , Effland M. J. , Kirk T. K.
Published: December 2004

This research examined culture parameters influencing the rate of degradation of lignin in lignocellulosic substrates by the Basidiomycete Phanerochaete chrysosporium. Thermomechanical pulps prepared from western hemlock (Tsuga heterophylla) and red alder (Alnus rubra) were chosen as model substrates. Degradation of lignin in shallow, liquid‐phase, stationary cultures was 10 times as rapid as in agitated cultures. Lignin degradation was at least 50% more rapid in cultures under 100% O2 than in those under air. Addition of 0.12% nutrient N (dry pulp basis) increased the rate of lignin degradation two‐ to fivefold; 1.2% added N at first suppressed, then stimulated, lignin degradation. Lignin in the alder pulp was degraded over five times as rapidly as in the hemlock pulp. Addition of glucose (35% of dry pulp) to the pulps containing 0.12% added N completely suppressed polysaccharide depletion during two weeks, but did not influence lignin degradation. The maximum rate of lignin degradation was 3%/day over a two‐week incubation, or approximately 2.9 mg/mg fungal cell protein/day. The influence of the examined parameters was in complete accord with those found earlier for synthetic 14C‐lignin metabolism by P. chrysosporium.
Investigation of fermentors with various contacting devices
Authors: Viesturs U. E. , Sturmains I. A. , Krikis V. V. , Prokopenko V. D. , Erickson L. E.
Published: December 2004

In this work, earlier published work on the development and investigation of fermentors with various contacting arrangements is reviewed. Methods and results of investigations on optimal construction of contacting plates are presented, and mass transfer and other characteristics of the performance of the equipment are discussed. Comparative estimates of various methods of determining mass transfer coefficients are presented. The construction and basic operating characteristics of several column fermentors with various contacting arrangements are described.
Surface aeration in a small, agitated, and sparged vessel
Authors: Chapman C. M. , Nienow A. W. , Middleton J. C.
Published: December 2004

In a recent publication, a technique was outlined for measuring surface aeration rates in an agitated vessels while sparging, and it was shown that surface aeration rates fall rapidly with increasing sparge rates. That work was conducted in a 0.61 m diam vessels. The work reported here was done in a small vessel (0.22 m diam) where surface aeration has been reported to be of particular significance. In general, the results obtained in the small vessel confirmed those in the large one and in addition were generally in good agreement with those recently published elsewhere for an almost identical geometry. For typical practical power inputs and sparge rates, the rate of surface aeration was never more than 20% of the sparge rate and generally less than 5%. These results indicate that surface aeration is of considerably less importance than has generally been believed following the findings of workers who estimated its effect by comparing KLa values under unsparged conditions with those when sparging.