bluuebunny/crossref_metadata_2025_split huggingface dataset:
The inhibition of β‐glucosidase activity in Trichoderma reesei C30 cellulase by derivatives and isomers of glucose
Authors: Woodward Jonathan , Arnold Susan L. 
Published: December 2004

AbstractThe inhibition of β‐glucosidase in Trichoderma reesei C30 cellulase by D‐glucose, its isomers, and derivatives was studied using cellobiose and ρ‐nitrophenyl‐β‐glucoside (PNPG) as substrates for determining enzyme activity. The enzymatic hydrolysis of both substrates was inhibited competitively by glucose with approximate Ki values of 0.5mM and 8.7mM for cellobiose and PNPG as substrate, respectively. This inhibition by glucose was maximal at pH 4.8, and no inhibition was observed at pH 6.5 and above. The α anomer of glucose inhibited β‐glucosidase to a greater extent than did the β form. Compared with D‐glucose, L‐glucose, D‐glucose‐6‐phosphate, and D‐glucose‐1‐phosphate inhibited the enzyme to a much lesser extent, unlike D‐glucose‐L‐cysteine which was almost as inhibitory as glucose itself when cellobiose was used as substrate. Fructose (2−100mM) was found to be a poor inhibitor of the enzyme. It is suggested that high rates of cellobiose hydrolysis catalyzed by β‐glucosidase may be prolonged by converting the reaction product glucose to fructose using a suitable preparation of glucose isomerase.
A comparative investigation of various cellulase assay procedures
Authors: Canevascini Giorgio , Gattlen Catherine 
Published: December 2004

AbstractThe cellulolytic activity of crude enzyme preparations from different cellulolytic fungi (namely Trichoderma viride, Trichoderma Koningii, Fusarium solani, Sporotrichum pulverulentum, Sporotrichum thermophile) was assayed comparatively with several common analytical procedures described in the literature. The investigation was carried out with the objective of evaluating, with raw culture filtrates, the different cellulase tests in relation to their specificity for endo‐ and exo‐cellulase action as well as to allow comparisons to be made between results from different research groups using different methods. (1)Cellulase activity was tested viscometrically as well as chemically (determination of reducing end groups) with different carboxymethylcelluloses as substrates. Essentially constant ratios between both kinds of activities were obtained, indicating that they are directly related. Nevertheless, international units of activity, calculated from viscometric measurements (glycosidic bonds broken per unit time) were considerably lower than international units deduced from the increase in reducing power (glucose equivalents liberated per unit time), this discrepancy most likely accounted for by the predominant influence of the exo‐cellulase component in cellulase tests based on the determination of reducing eng groups. (2) By estimating cellulase activity with insoluble cellulosic substrates no direct relationship could be established with the above‐described activities except in the case where the cellulose was amorphous. The ratio profile between activities thus obtained and endo‐cellulase activities determined viscometrically shows that some enzyme preparations (such as those from both Trichoderma sp.) are clearly more active than others against crystalline cellulose reflecting quantitative differences in enzyme composition. Nevertheless, for a biological understanding of cellulolysis. analytical procedures using crystalline celluloses are not adequate for specifically monitoring exo‐cellulase activity in crude enzyme solutions for essentially two reasons: (a) they are not sufficiently sensitive to detect small changes in enzyme activity during the early phase of growth, and (b) exo‐cellulase activity in crude enzyme solutions also depends on the endo‐cellulase activity present.
Improved method for the dynamic measurement of mass transfer coefficient for application to solid–substrate fermentation
Authors: André G. , Moo‐Young M. , Robinson C. W. 
Published: December 2004

AbstractA new method has been developed for the measurement of overall volumetric mass transfer coefficient (KLa) in gas‐liquid‐solid systems. This method is based on the examination of gas phase dynamics in a three‐phase contactor and consists of measuring continuously the response of the outlet gas composition to a step input change of CO2 in the inlet gas stream. The advantages and limitations of the new method are presented and its sensitivity is discussed on the basis of model predictions. Preliminary results on the implementation of the CO2 method are also reported. Experimental data obtained in a nonviscous electrolyte solution show that the proposed method compares favorably with the conventional dissolved oxygen technique, provided that a correction is made to take account of the difference in diffusivity of oxygen and carbon dioxide.
Kinetics of nitrification using a fluidized sand bed reactor with attached growth
Authors: Tanaka H. , Uzman S. , Dunn I. J. 
Published: December 2004

AbstractThe oxidation of ammonium ion to nitrite and nitrate ion (nitrification) has been studied in a laboratory scale fluidized sand bed reactor with attached microbial growth. The undefined population of Nitrobacteracea organisms were immobilized on the sand particles by natural attachment after 2–3 months of adaptation. General balance equations have been formulated for a recycle reactor and oxygenation tank system. Kinetic experiments in the reactor and in a microrespirometer have been analyzed in terms of double Michaelis–Menten rate expression for the nitrogenous reactants and dissolved oxygen. Dynamic simulation of the batch integral reactor system was used to establish the error in the kinetic constant which arose due to assuming differential behavior. Design guidelines have been developed for the oxygen requirements in terms of oxygen transfer coefficients, oxygen enrichment, and liquid recycle rate.
Immobilization of oxyreductases on inorganic supports based on alumina. Immobilization of lactate dehydrogenase on alumina by adsorption
Authors: Kovalenko G. A. , Shitova N. B. , Sokolovskii V. D. 
Published: December 2004

AbstractLactate dehydrogenase (LDH) was adsorbed on low‐(γ, η) and high ‐(θ, α) temperature forms of alumina. θ‐Al2O3 exhibited the greatest adsorption ability. The maximum adsorption value was 30 mg LDH/g of a carrier. The conditions for irreversible adsorption have been determined. An adsorption isotherm on θ‐Al2O3 for pH 6.0 has been obtained; the LDHads surface area and the carrier surface portion accessible to the enzyme molecules have been calculated. The reaction kinetic parameter were determined by taking into account the reaction proceeding in the intradiffusional region. The specific catalytic activity (Aspec) of LDHads at small surface coverage of θ‐Al2O3 is five times less than Aspec of the native enzyme and KMimm with respect to NADH exceeds KMnat by two orders or magnitude. The is evidence for a strong LDH–Al2O3 interaction and a considerable deformation of the enzyme globule. Aspec and KM decrease as the amount of the enzyme attached to the carrier increases. Due to adsorption. LDH becomes thermostable and durable. The LDHads samples conserve 20–40% of their activity at room temperature during a year.
Some properties of a papain–agarose reactor provided with a pH monitor
Authors: Ae. Sluyterman L. A. , Wijdenes J. 
Published: December 2004

AbstractA small reactor of immobilized papain was used to gain some knowledge about the effect of immobilization upon the reactivity of the enzyme towards one substrate and various types of inhibitors. A buffer solution containing benzoyl–arginine ethyl ester as substrate was run through a small column of papain immobilized by attachment to agarose beads. The pH of the effluent was measured continuously and provided the data used to calculate the substrate conversion during passage through the reactor. The operation of the system was checked by determining the substrate conversion as a function of flow rate. It proved to operate as theory demanded. The rate and extent of inhibition were measured after addition of various inhibitors to the buffer–substrate solution. The following quantities of immobilized papain were found to be equal within ±20% to those of the free enzyme in solution: the overall activity, the Km of benzoyl–arginine ethyl ester, the Ki of the competitive inhibitor benzoylamino‐acetonitrile, the rate of inactivation by chloroacetic acid and by chloroacetamide, the rate of activation by cysteine of the mixed disulfide of papain and cysteine, and the rate of spontaneous reactivation of the KCNO–papain adduct. The inactivation by KCNO proved to be strongly pH dependent. This may explain why the rate of the latter reaction is only 66% of the rate with free enzyme. It is concluded that the rates and equilibrium constants measured in the present reactor system are within ±20% of the values of the dissolved enzyme, provided that the reactions are not strongly pH dependent. Calculation showed there was no diffusion limitation.
Mixing time and oxygen transfer characteristics of double draft tube airlift fermentor
Authors: Margaritis Argyrios , Sheppard John D. 
Published: December 2004

AbstractDespite the increasing importance of airlift fermentors, very little published information is available on how the geometric configurations of the draft tubes and the air‐sparging system affect the mixing and oxygen transfer characteristics of the fermentor. A 14‐L air‐lift fermentor was designed and build with a fixed liquid height to diameter ratio of 1.5 utilizing four equally spaced air jets at the bottom. Two jet orifice sizes were used, 1.27 and 3.81 mm i.d., and for each jet size the following four geometric configurations were used: Single inner concentric draft tube, single outer concentric draft tube, two concentric draft tubes, and no draft tubes where the fermentor was operated as a shallow bubble column. It was found that the presence of draft tubes stabilized liquid circulation patterns and gave systemically higher mixing times than those obtained in the absence of draft tubes. In addition, the double draft tube geometry resulted in higher mixing times than the single draft tubes. For the power unit volume range 20 to about 250 W/m3 the larger 3.81‐mm orifices gave systemically higher kLa values than the smaller 1.27‐mm i.d. orifices. At 200 W/m3 the use of a single outer draft tube with the 3.81‐mm orifices resulted in 94% increase in kLa values over that obtained with no draft tubes. However, the effect of draft tube geometry on kLa values when the 1.27‐mm orifices were used was not significant. The air bubble formation characteristics at the jet orifices were found to be different, which reflected the differences observed in mass transfer and mixing characteristics. The power economy for oxygen transfer was found to be depend strongly on the orifice size and less on the geometric configuration of draft tubes.
Continuous enzymatic transformation in an enzyme membrane reactor with simultaneous NAD(H) regeneration
Authors: Wichmann Rolf , Wandrey Christian , Bückmann Andreas F. , Kula Maria‐regina 
Published: December 2004

AbstractMultienzyme reaction systems with simultaneous coenzyme regeneration have been investigated in a continuously operated membrane reactor at bench scale. NAD(H) covalently bound to polyethylene glycol with a molecular weight of 104 [PEG‐10,000‐NAD(H)] was used as coenzyme. It could be retained in the membrane reactor together with the enzymes. L‐leucine dehydrogenase (LEUDH) was used as catalyze for the reductive amination of α‐ketoisocaproate (2‐oxo‐4‐methylpentanoic acid) to L‐leucine. Format dehydrogenease (FDH) was used for the regeneration of NADH. Kinetic experiments were carried out to obtain data which could be used in a kinetic model in order to predict the performance of an enzyme membrane reactor for the continuous production of L‐leucine. The kinetic constants Vmax and Km of enzymes are all in the same range regardless of whether native NAD(H) or PEG‐10,000‐NAD(H) is used as coenzyme. L‐leucine was produced continuously out of α‐ketoisocaproate for 48 days; a maximal conversion of 99.7% was reached. The space‐time yield was 324 mmol/L day (or 42.5 g/L day).
Stability of immobilized yeast alcohol dehydrogenase
Authors: Ooshima Hiroshi , Genko Yumiko , Harano Yoshio 
Published: December 2004

AbstractThe effects of substrate on stabilities of native (NA) and three kinds of immobilized yeast alcohol dehydrogenase (IMA), namely PGA (the carrier; porous glass), SEA (agarose gel) prepared covalently, and AMA (anion‐exchange resin) prepared ionically, were studied. The following results were obtained. (1) The deactivations of NA and IMA free from the substrate or in the presence of ethanol obey the first‐order kinetics, whereas, in the presence of butyraldehyde, their deactivation behaviors are explained on the basis of coexistence of two components of YADHs, namely the liable E1, and the comparatively stable E2, with different first‐order deactivation constants. (2) A few attempts for stabilization of IMA were carried out from the viewpoint of the effects of crosslinkages among the subunits of YADH for PGA and the multibonding between the carrier and enzyme for SEA. The former is effective for the stabilization, whereas the later is not.
Effect of mixing duration and vacuum on methane production rate from beef cattle waste
Authors: Hashimoto Andrew G. 
Published: December 2004

AbstractThe effects of mixing duration and vacuum on methane production rates from anaerobically fermented beef cattle wastes were discussed. The results showed that continuously mixed fermentors produced significantly (P < 0.05) higher methane production rates than fermentors mixed two hours per day. However, the rates from the continuously mixed fermentors were only 8–11% higher than the intermittently mixed fermentors at six and four days hydraulic retention time (HRT), respectively. There was no significant difference between the vacuum and conventional fermentors at six days HRT, but there was a significant difference at four days HRT. The CH4 production rate of the vacuum fermentors was 5% higher than the conventional fermentors at four days HRT. The results of these experiments compared well with predicted CH4 production rates. These results suggest that there is little potential for increasing the fermentation rates of livestock wastes by increased mixing or vacuum.
The density of protein precipitates and its effect on centrifugal sedimentation
Authors: Bell D. J. , Heywood‐Waddington D. , Hoare M. , Dunnill P. 
Published: December 2004

AbstractIsoelectric soya‐protein precipitate densities were measured for mean particle sizes ranging from 3.4–65 μm by gradient centrifugation, centrifugation in water‐immiscible solvents, tracerdilution, gravity sedimentation of isolated particles. Coulter counter volume determination, and a comparison of Coulter counter and centrifugal sedimentation size distributions. The immiscible system and tracer dilution methods were both found to be unreliable due to experimental uncertainties. The Coulter counter volume measurement indicated the existence of a density‐size relationship with the aggregate density decreasing as the size increased. Comparison with sedimentation measurements showed that the Coulter counter measures 80% of the total aggregate volume for 6‐μm particles. The relation between aggregate density (ρa, kg m −3) and size (d, μm) was measured for isoelectric soya protein and casein precipitated by ammonium sulfate, using a comparison of the Coulter counter size distribution and centrifugal sedimentation. The functions were described for soya by

and for casein by

The gradient centrifugation method measured the buoyant density of hydrated protein precipitate which was independent of size, and is consistent with an aggregate structure consisting of primary particles. However, the aggregate structure was not described for all sizes by the theoretical cubic packing of hard‐sphere primary particles, nor by the successive random addition of primary particles. The density‐size functions indicated up to a fivefold difference in Stokes settling velocities compared to those calculated assuming a constant density difference.
Enzyme immobilization on tritylagarose
Authors: Cashion Peter , Javed Ali , Harrison Dolores , Seeley Jane , Lentini Victor , Sathe Ganesh 
Published: December 2004

AbstractA method is described for the immobilization on tritylated agarose or Sepharose columns of a wide spectrum of enzymes, including types useful in contemporary biochemistry/molecular biology, many of which have never before been reported as immobilized. The method involves the formation of noncovalent hydrophobic bonds between the enzymes and trityl groups which are attached to the agarose by means of ether bonds. The immobilization of calf intestinal and E. coli alkaline phosphatases to tritylagarose is reported in detail. Their binding strength, binding capacity, and long‐term stability (greater than six months) are described as a function of the salt concentration, pH, buffer type, and degree of agarose substitution. Homologies are noted between tritylagarose‐bound and membrane‐bound phosphatases. This method compares favorably with other methods, covalent or otherwise, reported to date, in terms of the enzyme immobilization yield (ca. 100%), the mildness of conditions, resulting, in most cases, in the retention of a high degree of activity, the ease and speed of the manipulations, and the long‐term stability of the immobilized enzyme. Further, it is noted that highly tritylated and crosslinked Sephadex G10 selectively and mildly removes detergents from enzyme solutions.
Oxygen transfer in broths of plant cells at high density
Authors: Tanaka Hideo 
Published: December 2004

AbstractThe rheological properties of the culture broths of some plant cells (Cudrania tricuspidata, Vinca rosea, and Agrostemma githago) at high density (10–18 g dry wt/L) were measured, and oxygen transfer in the broths in various bioreactors was investigated. The rheological properties of the broths were dependent on the size, specific gravity, and concentration of the cell aggregates contained in the broths. The broths were non‐Newtonian and pseudoplastic fluids. The flow behavior index n was fairly constant (0.53) and the consistency index K varied in proportion to the sixth‐to‐seventh power of the cell mass concentration M. The apparent viscosity μa of the broths was in proportion to the 6.5th power of M. The oxygen transfer in the broths was discussed on the basis of the results obtained for suspensions of granulated agars (agar concentration, 5.8%) in water, which were similar to the broths in rheological properties. The volumetric oxygen transfer coefficient kLa in the broths was dependent on μa(kLa ∝ μa−m) and decreased greatly at a certain apparent viscosity, μac. The values of m and μac were closely related to the aeration–agitation mechanisms of the bioreactors. The values of μac in aeration–agitation type bioreactors was larger than that in aeration‐type bioreactors, whereas for m, the reverse was true.
Enzyme degradation during drying
Authors: Luyben K. Ch. A. M. , Liou J. K. , Bruin S. 
Published: December 2004

AbstractDuring drying of food materials a multitude of chemical reactions and/or physical changes may occur. In this article attention is focused on one of these, namely, inactivation of enzymes during drying. The prediction of enzyme retention during drying is of interest to the pharmaceutical industry for the production of dry enzyme preparations and to the food processing industry in drying operations of food materials containing enzymes. In this article calculated enzyme retentions are presented for different drying histories and shapes of drying particles. In the numerical calculations it is assumed that enzyme degradation kinetics are first‐order reactions, of which reaction constants are known as a function of temperature and water concentration in the drying material. From the calculations, conclusions can be drawn about conditions favorable for high enzyme retentions, or for high enzyme degradations.
Maximum likelihood estimation of growth yields
Authors: Solomon B. O. , Erickson L. E. , Hess J. E. , Yang S. S. 
Published: December 2004

AbstractThis work is concerned with statistical methods to estimate yield and maintenance parameters associated with microbial growth. For a given dilution rate, an experimenter typically measures substrate concentration, oxygen utilization rate, the rate of carbon dioxide evolution, and biomass concentration. These correlated response variables each contain information about the maintenance and yield parameters of interest. A maximum likelihood estimator which combines this correlated information for the yield and maintenance parameters is proposed, evaluated, and tested on literature data. Both point and interval estimators are considered.
Studies on immobilized Saccharomyces cerevisiae. II. Effect of temperature distribution on continuous rapid ethanol formation in molasses fermentation
Authors: Ghose T. K. , Bandyopadhyay K. K. 
Published: December 2004

AbstractRecently, considerable interest has been shown in the study and analysis of immobilized cell reactors. One of the major uses of such a reactor system is expected to be in ethanol production from carbohydrates. One distinct disadvantage of this system is carbon dioxide gas holdup associated with unsteady‐state temperature distribution across the reactor. Taking into account the earlier published data and assuming steady‐state‐substrate balance, and unsteady‐state energy balance, and an average gas holdup of 20% with the heat retained by the gas neglected, the average reaction rate in the differential element was computed. Finally, a mathematical model to predict steady‐state temperature profile along the reactor was developed. It was verified with experimental data obtained from an immobilized yeast reactor column (1 m × 14.5 cm). The experimental data fit well those computed from the model within an accuracy of 5%.
Design of laboratory continuous‐culture equipment for accurate gaseous metabolism measurements
Authors: Brooks J. D. , Maclennan D. G. , Barford J. P. , Hall R. J. 
Published: December 2004

AbstractThe accuracy of kinetic and stoichiometric data obtained from most laboratory‐scale continuous‐culture equipment, particularly involving gaseous measurements, may be much lower than many workers realize, despite the use of good quality instruments. For example, errors in specific oxygen uptake measurements (QO2) easily can be as high as ±100%. This article assesses the accuracies of individual instruments and of the overall system in greater detail than has previously been reported and suggestions are made as to how the errors can be reduced to acceptable levels.
Production of NADP by immobilized cells with NAD kinase
Authors: Tanaka Yoshikazu , Hayashi Toru , Kawashima Koji , Yokoyama Tadashi , Watanabe Toshio 
Published: December 2004

AbstractBy the radiation‐copolymerization method with polyethylene glycoldimethacrylate (PGD) as a main polymerizable reagent, microbial cells of Brevibacterium ammoniagenes were immobilized with high specific activity of NAD kinase and high mechanical strength. The reagents used for the immobilization such as PGD, polyvinyl alcohol (PVA), and N,N′‐methylenebisacrylamide (Bis) did not inversely affect the enzyme activity. Freezing and irradiation treatment of the cell‐reagent solution did not inactivate the enzyme either, but longer freezing time or a lower irradiation dose (less than 400 krad) resulted in the unsatisfactory mechanical strength of the immobilized cells. Almost all of NAD and ATP consumed were converted into NADP within three hours reaction time. The drum reactor was found to be ideal for the reaction of immobilized cells, since it gave little mechanical stress to the immobilized cells for the effective mixing of the cells and the substrates. The immobilized cells were subjected to three hours reaction repeatedly for 30 times without any activity loss.