bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intensive use of biomass feedstock in ethanol conversion: The alcohol–water, vapor‐phase separation
Authors: Robertson George H. , Doyle Larry R. , Pavlath Attila E. 
Published: December 2004

AbstractFermentation of ethanol in a system whereby the biomass is used intensively (both to separate alcohol from water by vapor phase adsorption and to serve as the feedstock) is shown to be possible on theoretical grounds when the biomass is grain. The rationale for a vapor‐phase adsorption process as an alternative to distillation is shown to be energetically valid above 84 wt % ethanol. The capacity of grain in new vapor‐phase ambient adsorption processes was estimated experimentally with the finding that sufficient capacity exists for the intensive use but that the adsorption is dynamically controlled so that the grain form and particle size are important. Pretreatments such as explosive dehydration improve the transfer of water to the grain in adsorption with potential improvement in the efficiency of liquefaction and saccharification. At room temperature, these sorbents are not perfectly selective for water but adsorb ethanol which will be carried to the liquefaction, saccharification, and fermentation with the feedstock.
Immobilization of Saccharomyces cerevisiae by adhesion: Treatment of the cells by Al ions
Authors: Van Haecht J. L. , Bolipombo M. , Rouxhet P. G. 
Published: December 2004

AbstractThe adsorption of aluminum ions by Saccharomyces cerevisiae has been investigated by determining adsorption isotherms and electrophoretic mobility. The adsorption of aluminum ensures a neutralization of the cell surface charge and allows adhesion of the cells to glass and polycarbonate. Glass slides have been taken as a negatively charged model support, allowing the authors to study in detail the process of adhesion. The cells are simply pretreated by an aluminum solution near pH 4. Bringing the Al‐pretreated cells in contact with the support by sedimentation and washing the support and sediment makes it possible to obtain a single, dense, regular layer of cells adhering strongly to the support. Adhesion can also be obtained from a suspension flowing parallel to a vertical support, provided the flow velocity is sufficiently small; the amount of cells immobilized per unit support area is about one‐half that obtained by sedimentation. The immobilized cells show a specific activity for ethanol production from glucose which is similar to cells in suspension.
Studies on the mechanism of alkaline peroxide delignification of agricultural residues
Authors: Gould J. Michael 
Published: December 2004

AbstractAlkaline solutions of hydrogen peroxide partially delignify wheat straw and other lignocellulosic materials, leaving a cellulosic residue that is highly susceptible to enzymatic digestion by cellulase. The delignification reaction is strongly dependent upon the pH of the reaction mixture, with an optimum at pH 11.5–11.6, pKa for the dissociation H2O2 ⇌ H+ + HOO−. The data are consistent with a mechanism in which H2O2 decomposition products such as ·OH and O·, rather than H2O2 or HOO−, are the primary lignin oxidizing species. During the course of the delignification reaction, O2 is evolved from the reaction mixture indicating active H2O2 decomposition. At a given concentration of H2O2, the rate of O2 evolution is proportional to the amount of lignocellulosic substrate present in the reaction mixture. However, the total amount of O2 evolved is inversely proportional to the amount of substrate present, indicating that some of the peroxide oxygen becomes incorporated into lignin degradation products. The amount of peroxide oxygen incorporated can range as high as 2 O2 per lignin C9 unit, depending upon the initial concentration of lignocellulosic substrate.
Studies on batch and continuous cultures of Botryococcus braunii: Hydrocarbon production in relation to physiological state, cell ultrastructure, and phosphate nutrition
Authors: Casadevall E. , Dif D. , Largeau C. , Gudin C. , Chaumont D. , Desanti O. 
Published: December 2004

AbstractThe growth of the hydrocarbon‐rich alga Botryococcus braunii was studied under “air‐lift” conditions using batch and continuous cultures. Large variations in the physiological state of B. braunii were achieved in batch cultures and in continuous cultures with various dilution rates. The possible effects of these variations upon hydrocarbons (nature, relative abundance, location, level, productivity) and also on the production of exocellular polysaccharides were examined. The relationships between the physiological state of B. braunii and its hydrocarbon and polysaccharide production were discussed and compared with those generally observed in unicellular algae. The factors giving rise to the transition from high to low productivity stages were considered. To this end we examined, at first, the variations in cell ultrastructure and the resulting degeneration occurring during batch cultures. Afterward the parallel changes in some parameters of the medium (pH, phosphate level) were determined and their possible relationships with B. braunii growth and hydrocarbon production were discussed. The main features of phosphate nutrition in B. braunii and its effects on hydrocarbons were finally examined.
Application of a two‐compartment model to the wall growth of Pelobacter acidigallici under continuous culture conditions
Authors: Kreikenbohm Rainer , Stephan Wolfgang 
Published: December 2004

AbstractContinuous cultivation of Pelobacter acidigallici on gallic acid is accompanied by biofilm formation. Steady states can be obtained at dilution rates nearly twice the maximum growth rate. A two‐compartment model is presented which allows us to determine rate constants of attachment and detachment. The model is based on the assumption that the biofilm is fully penetrated by the substrate. At high dilution rates the outcome of our experiments is mainly determined by the attachment rate. The influence of the thickness of the biofilm is discussed in order to demonstrate the limitations of the model.
Modeling alkali consumption and digestibility improvement from alkaline treatment of wheat straw
Authors: Pavlostathis Spyros G. , Gossett James M. 
Published: December 2004

AbstractThe alkali consumption during alkaline treatment of wheat straw at ambient temperature was measured as a function of time, solids concentration, and alkali concentration. The maximum measured alkali consumption was 5.5 g NaOH/100 g TS over a period of 30 days of treatment. Chemical functional groups (e.g., acyl and carboxyl groups) were measured and compared with the observed alkali consumption. The kinetics of alkali consumption were studied and a model was developed which predicts alkali consumption reasonably well. Use of this model was made to predict biodegradability of alkali‐treated wheat straw, since a strong correlation was found to exist between alkali consumption and observed biodegradability. The method of bioconversion used was anaerobic digestion for methane production.
Application of scale‐down experiments in the study of kinetics of oxytetracycline biosynthesis
Authors: Bošsnjak Marijan , Stroj Alešs , Caurčcica Miljenko , Adamovica Vlasta , Glunčcica Zdravka , Bravar Danica , Johanides Vera 
Published: December 2004

AbstractScale‐down experiments in antibiotic biosynthesis were performed by transferring the corresponding amounts of fermentation broth from industrial to laboratory and pilot‐plant fermentors where the cultivation process was continued at different cultivation conditions. A previously proposed mathematical model was used to explain the experimental results. The effects of temperature, agitation‐aeration intensity, and medium addition during the process were investigated. Computer simulation data were fitted to the experimental data, and good agreement was found. As a consequence of increasing temperature up to 37°C, increases in the specific growth and autolysis rates as well as the specific rates of antibiotic synthesis and carbohydrate utilization were in evidence. Temperature increases of up to 40°C caused a lower oxytetracycline yield. The effect of increased oxygen transfer rate on oxytetracycline biosynthesis was more pronounced at higher temperatures than at lower cultivation temperatures. Culture differentiation (strain segregation) was also studied; it was found that the increased cultivation temperature could be favorable for the growth of biomass active in oxytetracycline biosynthesis. Results of experiments at the pilot‐plant scale showed that fed batch and repeated fed batch cultures could be successfully applied and the period of intensive antibiotic synthesis could be prolonged significantly.
Preparation of optically activeD‐arylglycines for use as side chains for semisynthetic penicillins and cephalosporins using immobilized subtilisins in two‐phase systems
Authors: Schutt Hermann , Schmidt‐Kastner Günter , Arens Alfred , Preiss Michael 
Published: December 2004

AbstractOptically activeD‐arylglycines, which are of interest for preparation of semisynthetic penicillins and cephalosporins, were isolated from the racemic mixtures of their derivatives using immobilized proteolytic enzyme subtilisin (EC No. 3.4.4. 16). The performance of these reactions in two‐phase systems, consisting of water and an immiscible organic solvent, improved the yield, purity, and economics of the process by increasing the substrate solubility and reducing the rate of nonenzymatic hydrolysis. The proportion of the organic phase can be as much as 75% of the overall volume without seriously impairing the enzymatic activity. The optically pureD‐andL‐arylglycines were liberated from theirD‐ andL‐derivatives by acid hydrolysis. The substituent influence of the various arylglycine derivatives on the rate of the enzymatic cleavage reaction was investigated.
Performance of hydrophobic chromatography in purification of α‐amylase
Authors: Sada Eizo , Katoh Shigeo , Inoue Tsuneo , Shiozawa Masami 
Published: December 2004

AbstractHydrophobic ligands were introduced onto agarose beads, and the adsorption capacity of the beads was measured. The adsorption capacity increased with increase in the carbon number of the ligand, ionic strength of the buffer solution, and temperature. Crude α‐amylase was purified with these hydrophobic adsorbents and the breakthrough and elution curves were estimated based on the mass transfer theory. Under strongly hydrophobic conditions, impurities contained in crude feeds and the lack of uniformity of packing caused by aggregation of beads affected adsorption and elution behaviors.
Purification and characterization of endo‐xylanases from Aspergillus niger. II. An enzyme of pl 4.5
Authors: Shei Juliana C. , Fratzke Alfred R. , Frederick Mary M. , Frederick James R. , Reilly Peter J. 
Published: December 2004

AbstractA homogeneous endo‐xylanase (1,4‐β‐D‐xylan xylanohydrolase, EC 3.2.1.8) was obtained from a crude Aspergillus niger pentosanase by chromatography with Ultrogel AcA 54, SP‐Sephadex C‐25 at pH 4.5, DEAE‐Sephadex A‐25 at pH 5.4, Sephadex G‐50, and SP‐Sephadex C‐25 with a gradient from pH 2.8 to pH 4.6. It was much more active on soluble than on insoluble xylan, yielding large amounts of unreacted xylan and a mixture of oligosaccharides with chain lengths from two to six. No xylose or L‐arabinose was produced. There was high activity on a xylopentaose through xylononaose mixture, but not on xylobiose, xylotriose, or xylotetraose. The enzyme had slight activity on untreated cellulose, carboxymethylcellulose, and pectin. Molecular weight was ca. 1.4 × 104, with an isoelectric point of 4.5 and an amino acid profile high in acidic but low in sulfur‐containing residues. In a 25‐min assay at pH 4.7, this endo‐xylanase was most active at 45°C, with an activation energy from 5 to 35°C of 33.3 kJ/mol. The optimum pH for activity was 4.9. Decay in buffer was first order, with an activation energy at pH 4.7 from 48 to 53°C of 460 kJ/mol. Optimum pH for stability was about 5.6, where the half‐life at 48°C in buffer was ca. 40 h.
Feast/famine growth environments and activated sludge population selection
Authors: Chiesa Steven C. , Irvine Robert L. , Manning John F. 
Published: December 2004

AbstractThe effect of feast/famine growth conditions on activated sludge cultures indicates that nonfilamentous cultures can be selected by providing proper substrate gradients and extended periods of endogenous metablism. Reactor operating strategies providing intermittently high substrate concentrations result in cultures characterized by high peak substrate and oxygen uptake activities, rapid settling rates, and high resistance to starvation. Sludge settleability can be manipulated using controlled variations in growth environment with corresponding changes noted in sludge activity. In combination with the low net growth rates associated with activated sludge systems, feast/famine environments would logically convey a selection advantage to microbes capable of readily assimilating substrate materials and maintaining viability during extended starvation periods.
Malic acid production by an electrochemical reduction system combined with the use of diaphorase and methylviologen
Authors: Maeda H. , Kajiwara S. 
Published: December 2004

AbstractA regenerating reaction combined with the use of native malate dehydrogenase, native diaphorase, methylviologen, NAD, oxalacetic acid as the substrate and lipoamide as a stabilizer was carried out in the presence of electrolysis. Consequently, malic acid was efficiently produced from oxalacetic acid in the regenerating reaction. A glassy carbon bead electrode was used as a cathode. Twenty four milliamperes were passed at a rotation speed of 500 rpm, 29.8 ± 0.3°C and −1.0 V. It was found that lipoamide has a stabilizing effect on malate dehydrogenase and diaphorase. Low concentration (50 μM) of NAD was also effective for the stabilization of malate dehydrogenase. NADH regeneration activity based on malic acid production rate was 4.7 U/mg of the enzyme protein of the commercial diaphorase preparation. The current efficiency was more than 74%, compared with the theoretical yield, in the presence of enough oxalacetic acid.
Use of cell affinity chromatography for separation of lymphocyte subpopulations
Authors: Hertz C. M. , Graves D. J. , Lauffenburger D. A. , Serota F. T. 
Published: December 2004

AbstractWe describe the use of affinity chromatography for separation of cell populations that do not differ significantly with respect to gross physical properties such as size, density, or charge. Cell affinity chromatography exploits differences in cell surface macromolecules by passage of mixtures of cell populations through a column containing beads to which are attached chemical ligands with specific binding affinity for particular cell surface receptors. In this article we focus on the application of this concept to separation of mature T lymphocytes from peripheral blood. This serves as a model for the separation of these cells from bone marrow in order to prevent graft‐vs.‐host disease in bone marrow transplantation. However, the concept of cell affinity chromatography should find more general widespread utility in a variety of biotechnological applications. Thus, we introduce a simple theoretical framework which is necessary in order to understand the results that might be expected in any given situation. Finally, we use this theory to provide a tentative explanation for experimental observation of the effects of temperature and flowrate on the degree of separation achieved for our current pplication.
Structured modeling of the anaerobic digestion of biomass particulates
Authors: Bryers J. D. 
Published: December 2004

AbstractAnaerobic digestion of biological organic particulates to methane has been described by a structured mathematical model based on multiple‐reaction stoichiometry, conventional material balances, and liquid phase equilibrium chemistry. A general stoichiometric treatment for any set of multiple biological reactions is derived based on a unit mass of oxggen equivalents of the reactions limiting substrate. The model agrees well with two existing experimental studies of anaerobic digestion of biomass particulates. Hypothetical computer simulations are presented to illustrate possible instabilities of the anaerobic process under various operating scenarios.
Kinetics of chitinase production. I. Chitin hydrolysis
Authors: Young Manuel E. , Bell Richard L. , Carroad Paul A. 
Published: December 2004

AbstractAs part of the development of a comprehensive mathematical model for chitinase production by Serratia marcescens QMB 1466 growing on chitin, the different mass transport and kinetic steps involved during chitin hydrolysis were studied. The experimental results for the hydrolysis of chitin by a crude preparation of chitinase show a system kinetically limited by the overall rate of chitin hydrolysis. This rate is linearly related to the concentration of enzyme adsorbed on the chitin particle. Adsorbed and bulk enzyme concentration were found to be related through a Langmuir type of isotherm.
Performance of an upflow anaerobic reactor combining a sludge blanket and a filter treating sugar waste
Authors: Guiot S. R. , van den Berg L. 
Published: December 2004

AbstractA new hybrid reactor, the upflow blanket filter (UBF), which combined on open volume in the bottom two‐thirds of the reactor for a sludge blanket and submerged plastic rings (Flexiring, Koch Inc., 235 m2/m3) in the upper one‐third of the reactor volume, was studied. This UBF reactor was operated at 27°C at loading rates varying from 5 to 51 g chemical oxygen demand (COD)/L d with soluble sugar wastewater (2500 mg COD/L). Maximum removal rates of 34 g COD/L d and CH4 production rates of 7 vol/vol d [standard temperature and pressure (STP)] were obtained. The biomass activity was about 1.2 g COD/g volatile suspended solids per day. Conversion (based on effluent soluble COD) was over 93% with loading rates up to 26 g COD/L d. At higher loading rates conversion decreased rapidly. The packing was very efficient in retaining biomass.
Mathematical simulation of a biofilm process
Authors: Benefield Larry , Molz Fred 
Published: December 2004

AbstractA mathematical model has been developed for a fixed‐film biological process (film flow over a flat plate) that describes bulk liquid transport, diffusional transport of oxygen and organics across a stagnant film, diffusional transport of oxygen and organics into the biofilm, biochemical reactions by the individual cells within the biofilm, biofilm growth, and cell density changes within the biofilm due to cellular decay. Simulation studies are presented to show how contact time and diffusion layer thickness affect process performance.
Modeling of enzyme immobilization in porous membranes
Authors: Hossain Md. M. , Do D. D. 
Published: December 2004

AbstractThis article deals with the mathematical modeling of the process of enzyme immobilization in porous membranes. During the initial period, an analytical solution is available to extract the rate constant for immobilization. Beyond this period, the model equations are solved numerically to yield the transient response of the enzyme concentration in the immobilizing solution and also the evolution of the enzyme loading profile inside the membrane. It is found that the immobilization practically ceases even through the attachment sites are still available within the membrane.
Importance of agitation in acetone‐butanol fermentation
Authors: Yerushalmi Laleh , Volesky Bohumil 
Published: December 2004

AbstractThe specific rates of anaerobic solvent production byClostridium acetobutylicumincreased with increasing fermentor impeller speed from 190 to 340 rpm (NRe= 3.93 × 104). The maximum values were 5.54, 3.85, and 0.8 mmol/h · g cell for butanol, acetone, and ethanol, respectively. Corresponding rates for respective gases produced were 11.60 and 15.88 mmol/h · g cell for H2and CO2. Further increases in agitation speed resulted in generally decreasing specific production rates to the point of inactive fermentation at 560 rpm. A competition observed between the cellular subsystems for butanol + butyric acid and biomass biosynthesis was evaluated through expressing the energetic yield coefficients. An imbalance between the production and outflux of the former metabolites is apparently further enhanced by a mechanical damage of the cells at high shear rates. A correlation was developed between the production of gases and solvents pointing at both H2‐to‐solvent as well as CO2‐to‐solvent ratios following the same pattern, peaking at 410 rpm.
Biotransformation of 3‐methoxy‐8,14‐seco‐1,3,5(10),9(11) estratetraen‐14,17‐dione (secodione) to its 17β‐hydroxy derivative (secol) using immobilized yeast cells (Pichia farinosa Y‐118)
Authors: Bihari Vinod , Joshi A. K. , Khan A. W. , Vora V. C. 
Published: December 2004

AbstractThe yeast cells of Pichia farinosa Y‐118 were immobilized in polyacrylamide gel and used for 17 β‐oxidoreduction of secondione to secol. The loss of hydroxysteroid oxidoreductase activity of cells was found to be insignificant during immobilization. The preparation exhibited greater temperature stability as compared to free cells. The ratio of reaction volume to the volume of immobilized biocatalyst in the range 1.4−1.9 was found to be satisfactory for the reaction conditions studied. This ratio played a significant role in the stability of the catalyst particle, since beyond a critical value the disintegration of gel granules was rapid resulting in sharp decline of activity. The immobilized cell preparation could be used 50 times over a period of 100 days without loss of activity. However, the activity declined in further reuses, leaving the preparation 50 and 35% active after its 60th and 70th uses, respectively.
Thermophilic anaerobic digestion of high strength wastewaters
Authors: Wiegant W. M. , Claassen J. A. , Lettinga G. 
Published: December 2004

AbstractInvestigations on the thermophilic anaerobic treatment of high‐strength wastewaters (14‐65 kg COD/m3) are presented. Vinasse, the wastewater of alcohol distilleries, was used as an example of such wastewaters. Semicontinuously fed digestion experiments at high retention times revealed that the effluent quality of digestion at 55°C is comparable with that at 30°C at similar loading rates. The amount of methane formed per kilogram of vinasse drops almost linearly with increasing vinasse concentrations. This can be attributed to increasing concentrations of inhibitory compounds, resulting in increasing volatile fatty acid (VFA) concentrations in the effluent. The treatment of vinasse was also investigated using upflow anaerobic sludge blanket (UASB) reactors. Thermophilic granular sludge, cultivated on sucrose, was used as seed material. The sludge required a 4‐month adaptation period, during which the size of the sludge granules decreased significantly. However, the settling characteristics remained satisfactory. After adaptation, high loading and methane generation rates could be accommodated at satisfactory treatment efficiencies, namely, 86.4 kg COD/m3 day and 26 m3 CH4(STP)/m3 day, respectively. As in the semicontinuously fed digesters, the effluent VFA concentrations were virtually independent of the loading rates applied, indicating that the toxicity of the vinasse is more important than the loading rate in determining the efficiency of the conversion of vinasse to methane.