bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional evaluation of the white‐rot fungus Sporotrichum pulverulentum as a feedstuff to rats, pigs, and sheep
Authors: Thomke S. , Rundgren M. , Eriksson S.
Published: December 2004

The production of single‐cell protein (SCP) based on cheap carbon sources such as spent liquor from paper mills is of interest for different reasons. The White‐rot fungus (Sporotrichum pulverulentum) has earlier been shown to degrade cellulose and lignin. The nutritive value of this fungus was investigated with rats, pigs, and sheep. The effect of different drying process was evaluated on rats. Experiments with piglets, growing pigs, and sheep were aimed at getting primary information on nutritive parameters with domestic animal species, Chemical analysis of S. pulverulentum showed that the sum of the amino acids corresponded to 70% and ammonia, GABA, and glucosamine to 20% of its crude protein content. Differences between drying treatments in their effect on protein digestibility were not noted. From a protein quality viewpoint, a tendency toward superiority was noted for two of the drying processes. The amino acid digestibility of S. pulverulentum was inferior to values for soybean oil meal given in textbooks. The piglet experiment confirmed the lower nutritive value of S. pulverulentum compared with soybean oil meal. in the piglet stage a content of metabolizable energy of S. pulverulentum was found which corresponded to 60% of that for soybean oil meal. With increasing age the ability of pigs to utilize the fungus increased. The limited nutritive value for monogastric animals is most certainly caused by the cell‐wall structure of S. pulverulentum with poor digestibility of the carbohydrates. The experiment with sheep showed more satisfactory results than with monogastric species, with digestibility of crude protein of 82% and a content of metabolizable energy of 70% of soybean oil meal.
Morphological and ultrastructural study of the cell envelope of thermophilic and acidophilic microorganisms as compared to Thiobacillus ferrooxidans
Authors: Berry V. K. , Murr L. E.
Published: December 2004

The cell envelope of a Sulfolobus‐like microorganism has an arrayed hexagonal subunit structure, a double‐layered cytoplasmic membrane, and a hollow periplasmic space between the plasma membrane and the outermost arrayed layer. A dense peptidoglycan layer outside the plasma membrane found in the case of Thiobacillus ferrooxidans was not seen. The cell envelope of a thermophile isolated from a leaching environment has a well‐defined envelope with two well‐stained layers distinclty seen. While the peptidoglycan layer is also not seen in this thermophile, a long flagellum similar to that in the case of T. ferrooxidans is present. The presence of pili in the Sulfolobus‐like organism and its arrayed subunit cell envelope structure could account for the organism's selective attachment to sulfide phases in the leaching of low‐grade ores. The observations of a well‐defined cell envelope in the two thermophiles is consistent with the structure‐function relationship previously established for T. ferrooxidans.
Relationship between phosphate stress, effluent quality, and observed cell yield in a pure‐oxygen activated‐sludge plant
Authors: Verstraete W. , Vissers W.
Published: December 2004

The effect of continuous and discontinuous phosphate stress on the observed cell yield coefficient was investigated in a petrochemical pure‐oxygen wastewater treatment plant. A continuous phosphate stress in the activated‐sludge system resulted in a reduction of sludge production by 36%, but no improvement of the effluent quality was noticed compared with that of nonstress treatment. However, discontinuous phosphate stress produced a high‐quality effluent due to the excellent setting settling properties of the sludge flocs. In addition, the observed cell yield coefficient and concomitantly the sludge production remained 45% below normal. The introduction of the discontinuous phosphate stress in the pure‐oxygen activated‐sludge plant at the BP Chemicals works in Antwerp resulted in a 24% reduction of the total wastewater treatment operating costs.
Microrecirculation reactor system for characterization of immobilized enzymes
Authors: Taylor James B. , Swaisgood Harold E.
Published: December 2004

A differential microrecirculation reactor was developed for kinetic analysis of both soluble and immobilized enzymes. The reactor system was easliy fabricated with in the laboratory from readily available materials. The disposable, small reactors allowed for in situ weight determination of the enzyme beads. Routinely, only a 1 ml liquid volume of substrate was used for each kinetic assay. The reactor system was also used for determination of partition coefficients. Both uses of the reactor system required only 5–10 min for completion of a given determination.
Total containment of a continuous‐flow zonal centrifuge
Authors: Gooders A. P. , Webb N. L. , Allen G. J. , Richards B. M.
Published: December 2004

A continuous‐flow, high throughput, turbine‐driven zonal centrifuge has been contained for use with biologically hazardous materials. The centrifuge and all ancillary equipment are enclosed in three sealed cabinets that are maintained at negative pressure, decontaminated with ethylene oxide, and provide cooling for the process fluids. Sample handling is semiautomated and remotely controlled for ease of operation and includes an automated decontamination system. The centrifuge subsystems can be decontaminated prior to an engineer servicing the machine, and apparatus is provided for absolute filtration of the centrifuge turbine exhaust.
Influence of engineering variables upon the morphology of filamentous molds
Authors: van Suijdam J. C. , Metz B.
Published: December 2004

A modal has been described for the influence of growth rate and shear stresses in the fermentor upon the morphology of filamentous molds. The main concept of this model is the dynamic equilibrium between growth and breakup of the hyphae. The latter has been approached according to well‐known engineering theories for dispersion of physical systems. Experiments to verify the model with a strain of Penicillium chrysogenum in batch and continuous culture revealed that the length of the mycelial particles increased with increasing growth rate and decreased with increasing power input her unit mass in the fermentor. Although this was qualitatively in agreement with the presented model, quantitatively the model had to be rejected. Variation of the tensile strength of the hyphae with age and culturing conditions could have been one of the causes of disagreement. Oxygen tension, varied independently from stirrer speed, in the range of 12–300 mm Hg was shown to have no influence upon the morphology. With respect to the question of possibly using high‐energy inputs in industrial mold fermentation in order to decrease hyphal length and suspension viscosity, it was concluded that this is of little practical value. A substantial decrease in hyphal length requires an enormous increase in energy input.
Raw materials evaluation and process development studies for conversion of biomass to sugars and ethanol
Authors: Wilke C. R. , Yang R. D. , Sciamanna A. F. , Freitas R. P.
Published: December 2004

A range of cellulosic raw materials in the form of agricultural crop residue was analyzed for chemical composition and assessed for potential yields of sugars through chemical pretreatment and enzymatic hydrolysis of these materials. Corn stover was used as a representative raw material for a preliminary process design and economic assessment of the production of sugars and ethanol. With the process as presently developed, 24 gal ethanol can be obtained per ton of corn stover at a processing cost of about $1.80/gal exclusive of by‐product credits. The analysis shows the cost of ethanol to be highly dependent upon: (1) the cost of the biomass, (2) the extent of conversion to glucose, (3) enzyme recovery and production cost, and (4) potential utilization of xylose. Significant cost reduction appears possible through further research in these directions.
Characterization of anaerobic microbial culture with high acidogenic activity
Authors: de la Torre Irma , Goma Gérard
Published: December 2004

The mixed cultures which were used were isolated from municipal sludge digesters, and the production of organic acids (acetic, propionic, butyric, etc.) from carbohydrates was tested. The behavior of the reference population (culture R) obtained directly from the sewage treatment plant, is compared to that obtained after three months in a plug‐flow reactor (Gradostat fermentor) without pH control (culture A) and after six months with pH control (culture B). For culture B, the specific rate of acid production is related to the cell growth rate by (1/X)rp= 17 µ + 1.6 with a maximal acid concentration of 40 g/liter. The batch culture yields are improved from 0.36g/g for the initial culture (R) to 0.72 g/g for culture B after six months in continuous culture, and 0.8 g/g in plug‐flow continuous culture. The productivity of organic acids reaches 1.7 g/liter·hr. It is suggested that the acidogenic fermentation, the first step of methanogenesis, is a potential process to produce acetic, propionic, and butyric acids.
Alcoholic fermentation: On the inhibitory effect of ethanol
Authors: Novak M. , Strehaiano P. , Moreno M. , Goma G.
Published: December 2004

The inhibitory effect of ethanol is studied during alcoholic fermentation in strict anaerobiosis (initial dissolved oxygen stripped by gasing pure nitrogen). It is demonstrated that the ethanol produced during the batch fermentation is more inhibitory than the added ethanol (in the range of 0 to 72.6g/liter). By analogy with noncompetitive enzyme kinetic inhibition, the inhibition constant for added ethanol is 105.2 g/liter and 3.8 g/liter for produced ethanol, which exhibits the same inhibition effects in all experiments where ethanol was added. The measurement of the intracellular alcohol concentration can explain the dual inhibitory effects of ethanol.
Regulation phenomena in methanol consuming yeasts: An experiment with model discrimination
Authors: Bajpai R. K. , Reuß M. , Held W.
Published: December 2004

Assimilation as well as dissimilation of methanol in yeasts takes place through its oxidative intermediate formaldehyde which is several times more toxic to the growth of microorganisms than methanol itself. Still, the role of formaldehyde, produced during methanol assimilation, upon growth of yeasts is not clear. In the present paper, an attempt has been made to throw some light upon this aspect. Starting with a basic frame work for methanol uptake by yeasts, several models were developed assuming different modes of regulation of key enzymes by methanol and/or formaldehyde. The main feature of the basic framework consists in consideration of two routes for oxidation of formaldehyde to CO2, one associated and the other not associated with production of energy. Further, the rate of energy production form the energy‐associated oxidation of formaldehyde is assumed to be controlled by the rate of energy consumption by anabolic reactions. The models were discriminated by subjecting these to biological constraints. As a result, the successful model suggests that in spite of higher inherent toxicity of formaldehyde, methanol exerts the controlling influence upon growth under normal conditions.
Dialysis continuous process for ammonium lactate fermentation: Simulated prefermentor and cell‐recycling systems
Authors: Stieber R. W. , Gerhardt Philipp
Published: December 2004

A generalized mathematical model, previously developed and experimentally validated, was modified and used to computer‐simulate the outcomes of adding two systems for increasing the concentration of cell mass in the fermentor, and thereby the rate and extent of substrate conversion, in a dialysis continuous process for the ammonium lactate fermentation of deproteinized whey. The addition of a nondialysis continuous prefermentor would not improve the process. However, the addition of cell retention time would be reduced ninefold, and the extent of converting substrate to product would be increased 25% and accomplished almost entirely by maintenance metabolism.
Enzyme deactivation in fixed bed reactors with michaelis‐menten kinetics
Authors: Do Duong D. , Weiland Ralph H.
Published: December 2004

Rate expression for enzyme poisoning which are consistent with a Michaelis‐Menten main reaction are used to analyze the performance of a fixed bed reactor containing immobilized enzyme. When enzyme deactivation results from the irreversible bonding of a product molecule to an existing substrate‐enzyme complex, it is shown that minimum enzyme activity can occur in the interior of the bed, well away from the ends. This suggests that bed sectioning techniques may enable direct evaluation of fundamental poisoning mechanisms.
Stabilization of chloroplast by radiation‐induced immobilization with various glass‐forming monomers
Authors: Youshii F. , Fujimura T. , Kaetsu I.
Published: December 2004

The effect of immobilization with various glass‐forming monomers on the stability of PS II activity of spinach chloroplast was investigated. PS II activity (O2 evolution due to the Hill reaction) was reduced very slightly by the addition of monomers including polyethyleneglycol (PEG). Immobilization of chloroplast was done with hydrophobic monomer as well as hydrophilic monomer and activity of immobilized chloroplast increased with decreasing monomer concentration as far as the polymerization was possible. The activity of immobilized chloroplast was very high and it decayed far more gradually with the storage time in comparison with the decay of unimmobilized chloroplast and was retained more than 30 days. The optimum monomer concentration for immobilization was about 10%. Thermostability of chloroplast also increased greatly by immobilization with these monomers, especially hydrophilic monomers.
Use of the centrifugal separation technique in manufacturing a bioinsecticide based on Bacillus thuringiensis
Authors: Zamola Branimir , Valles Paolo , Meli Giuseppe , Miccoli Pietro , Kajfež Franjo
Published: December 2004

We have examined the possibility of separating residual Bacillus thuringiensis medium from crystal endotoxin and determined an optimal flow rate of fermentation broth through a disk centrifuge in order to make a total separation of the residue of nutritive medium, containing pathogenic toxins, from the endotoxin and spores.
Bioenergetic analysis of mixotrophic growth in Chlorella vulgaris and Scenedesmus acutus
Authors: Ogawa Takahira , Aiba Shuichi
Published: December 2004

The specific growth rate of Chlorella vulgaris in the presence of glucose (mixotroph) was always larger than that in autotroph when the light intensity was less than 10 klux. However, Scenedesmus acutus behaved differently, i.e., when the light intensity was more than 6 klux, the specific growth rate in mixotroph became smaller than that in autotroph. Cellular contents of chlorophyll a and b in Scenedesmus acutus that deteriorated more markedly in mixotroph than those of Chlorella vulgaris could account for these different growth behaviors. In other words, mechanisms relevant to the photosynthesis and the oxidative phosphorylation of glucose seem to function independently with respect to Chlorella Vulugaris.
Fermentors with the power introduced by aerating gas
Authors: Viesturs U. E. , Sturmanis I. A. , Krikis V. V. , Prokopenko V. D. , Erickson L. E.
Published: December 2004

In the present work methods and results of investigations on optimal construction of fermentor elements by multifactor planning at a random number of levels of any factor are presented. The optimal design of column fermentor of 0.02–100 m3 volume with sieve plates containing downcomers and with power introduced by aerating gas has been worked out. Several alternative designs have been compared by examining mass transfer rates, power requirements, and other operating characteristics. Several fermentor designs with the power introduced by aerating gas are discussed with respect to their performance for cultivating various microorganisms (yeast and bacteria).
Procedure for isolation of Thienamycin from fermentation broths
Authors: Treiber Laszlo R. , Gullo Vincent P. , Putter Irving
Published: December 2004

An improved process for the isolation of thienamycin, produced by the actinomycete Streptomyces cattleya, has been developed. The isolation procedure consists of three chromatographic steps, volume reduction by reverse osmosis between the steps, and freezedrying for obtaining the final product. The chromatographic steps are as follows: (1) ion exchange chromatography on Dowex 1 × 2 resin in the bicarbonate cycle, (2) gel chromatography on Dowex 1 × 2 resin in the chloride cycle, (3) reverse phase chromatography on XAD‐2 resin. This procedure is useful for processing large volumes of fermentation broth.
Alcohol fermentation of sweet potato. Membrane reactor in enzymatic hydrolysis
Authors: Azhar A. , Hamdy M. K.
Published: December 2004

Use of Ultrafiltration membrane systems in stirred cell and in thin‐Channel systems for immobilizing enzyme (sweet potato intrinsic and β‐amylase) in hydrolysis of sweet potato through a continuous operation mode were studied. Both the filtration rate and reducing sugars, produced as the result of enzymatic hydrolysis, decreased with the filtration time. The immobilized enzymes in the thin‐channel system showed a much better performance compared to that in the stirred cell system. Addition of crystalline sweet potato β‐amylase to the sweet potato increased both the filtration rate and reducing‐sugars content. Alcoholic fermentation of the filtrate resulted in an alcohol content of 4.2%. This represented fermentation of 95% of the sugars with an efficiency of 88%.
Variation of bagasse crystallinity and cellulase activity during the fermentation of Cellulomonas bacteria
Authors: Enríquez A. , Montalvo R. , Canales M.
Published: December 2004

A characteristic behavior of the fermentation process was observed during the growth of Cellulomonas on sugarcane bagasse. At the early stage of the fermentation the crystallinity index of bagasse increased, suggesting that the major metabolized fraction corresponded to the hemicellulose during this stage. Some time later the crystallinity achieved a steady state and then deceased, which indicated that the most complex structure of bagasse was being attacked. The analysis of the cellulolytic activity of extracellular enzyme in the medium showed a sharp increase followed by an abrupt leveling off and decline in activity. These results along with the reduction of crystallinity index and bagasse utilization (70%) justify the assumption that the C1 component was present in the cellulase complex synthesized by the bacteria.
Membrane reactor for enzymatic hydrolysis of cellobiose
Authors: Hong J. , Tsao G. T. , Wankat P. C.
Published: December 2004

A pressurized, stirred vessel attached with an ultrafiltration membrane was used as a membrane reactor, Cellobiose hydrolysis by cellobiase was carried out and theoretically analyzed in terms of steady‐state conversion and flow rate through the membrane. When the flow rate exceeds a critical value, a significant fraction of the enzyme inside the reactor is localized in the concentration polarization layer where shear from stirring is high. Consequently, enzyme deactivation inside the concentration polarization layer is accelerated and the conversion decreases due to an exchange of active enzyme in bulk with deactivated enzyme in the polarization layer via convection and back diffusion. Successful operation can be obtained at flow rates lower than the critical point to avoid the polarization and thus the deactivation. It is shown that 6.5 L of 2 mg/mL of cellobiose solution is hydrolyzed to glucose with a conversion of 91% in 20 h with 1.617 mg of cellobiase enzyme, in a reactor attached with a PM 10 membrane of an effective surface area of 39.2 cm2.
Kinetics of multiproduct fermentations
Authors: Lam Jeffrey C. , Ollis David F.
Published: December 2004

A simple model for biomass, product, and substrate evolution proposed previously for batch polysaccharide fermentations is extended to multiproduct fermentations. The examples involve Clostridium thermocellum, (ATCC 27405) fermentations of glucose to four products (ethanol, acetic, formic, and lactic acid), of fructose to two products (ethanol and acetic acid), and of cellobiose to two products (ethanol and acetic acid). In all cases, parameter evaluation was carried out in a serial deterministic procedure.
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

The 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

The 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

A 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

The 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

Lactate 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

A 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

Despite 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

Multienzyme 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

The 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

The 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

Isoelectric 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

A 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

The 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

During 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

This 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

Recently, 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

The 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

By 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.
Growth models of the continuous bacterial leaching of iron pyrite by Thiobacillus ferrooxidans
Authors: Chang Yun Chea , Myerson Allan S.
Published: December 2004

The leaching of iron pyrite by Thiobacillus ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.012–0.22 h−1), pyrite surface areas (18–194 m2/L), and inlet soluble substrate (Fe2+) concentrations (0–3000 ppm). The bacterial leaching rate was found to increase with increasing pyrite surface area, dilution rate, and inlet Fe2+ concentration. The concentration of bacteria in solution was related to the concentration of bacteria attached to the pyrite surface by a Langmuir‐type adsorption‐desorption relation. Fitting the experimental data to this relation yielded a value for the area occupied per bacterium of 86 μm2. This result is consistent with the concept of preferential bacterial attachment of certain sites on the solid. A bacterial growth model was developed that included both bacterial growth in solution and growth of bacteria attached to the pyrite surface. The specific growth rate of the attached bacteria was calculated from this model and was found to increase with increasing solid dilution rate and to decrease with increasing pyrite surface area and soluble substance concentration. An explanation of these results based on an active‐inactive site mechanisms was also developed.
Hydrogen fluoride saccharification of wood: Lignin fluoride content, isolation of α‐D‐glucopyranosyl fluoride and posthydrolysis of reversion products
Authors: Hardt Haim , Lamport Derek T. A.
Published: December 2004

Wood chips from bigtooth aspen (Populus grandidentata Michx.) were saccharified by reaction with liquid hydrogen fluoride either anhydrous or containing up to 10% v/v water. The reaction products were separated into a solid lignin fraction and a water‐soluble saccharide fraction. The fluoride content of the lignin (determined after alkaline fusion) was initially about 1 mg/g wood, but was lowered to 0.1 mg/g wood by grinding and washing. Thus little or no chemical binding of fluoride to lignin occurred during hydrogen fluoride (HF) solvolysis. Analysis of the water‐soluble fraction by gel filtration on Biogel P2 columns showed a range of low‐molecular‐weight oligosaccharides and only 10–20% sugar monomers. Thus considerable reversion occurred during HF evacuation. Posthydrolysis conditions were optimized for these reversion products by varying temperature and acid concentration. Optimal conditions at 1 h were 140°C with 100mN sulfuric acid or 225mN Hydrofluoric acid resulting in monomer yields of > 90% for 0.5% sugar solutions and > 80% for 10% sugar solutions. After reaction of pure cellulose (Filter paper) with hydrogen fluoride in the absence of water, and terminating the reaction with calcium carbonate, the reaction intermediate α‐D‐glucopyranosylfluoride was isolated with a maximal yield of 0.2 g/g paper. Upon purification via paper chromatography glucosylfluoride was identified by its specific rotation and also by gas chromatography‐mass spectrometry of its tetra‐O‐trimethylsilyl derivative.