bluuebunny/crossref_metadata_2025_split huggingface dataset:
A continuous, farm‐scale, solid‐phase fermentation process for fuel ethanol and protein feed production from fodder beets
Authors: Gibbons William R. , Westby Carl A. , Dobbs Thomas L. 
Published: December 2004

AbstractFuel ethanol (95%) was produced from fodder beets in two farm‐scale processes. In the first process, involving conventional submerged fermentation of the fodder beets in a mash, ethanol and a feed (PF) rich in protein, fat, and fiber were produced. Ethanol yields of 70 L/metric ton (7 gal/ton) were obtained; however, resulting beers had low ethanol concentrations [3–5% (v/v)]. The high viscosity of medium and low sugar, beet mashes caused mixing problems which prevented any further increase of beet sugar in the mash. The severely limited the maximum attainable ethanol concentration during fermentation, thereby making the beer costly to distill into fuel ethanol and the process energy inefficient. In order to achieve distillably worthwhile ethanol concentrations of 8–10% (v/v), we developed and tested a solid‐phase fermentation process (continuous). In preliminary trials, this system produced fermented pulp with over 8% (v/v) ethanol corresponding to an ethanol yield of 87 L/metric ton (21 gal/ton). Production costs with this novel process are $0.47/L ($1.77/gal) and the energy balance is 2.11. These preliminary cost estimates indicate that fodder beets are potentially competitive with corn as an ethanol feedstock. Additional research, however, is warranted to more precisely refine individual costs, energy balances and the actual value of the PF.
Optimization of a reactor assembly for the production of 6‐APA from penicillin‐V
Authors: Karlsen Lars G. , Villadsen John 
Published: December 2004

AbstractThe design and operation of an industrial penicillin‐V deacylation reactor is simulated, using a kinetic expression and mass transport parameters for the immobilized enzyme particles which were determined experimentally in a previous study. It is desirable to use a series of equalsized plug flow reactors with pH control at the entrance to each reactor, and with a possibility of recycling reactant in each reactor. These measures are necessary to avoid a steep pH profile through the reactor; the deacylation reaction is accompanied by an increase of acidity of the reaction medium, and H+ is a strong inhibitor and may deactivate the enzyme. The optimization study which is carried out at a fixed penicillin conversion of x = 0.99 shows that it is uneconomical to use penicillin feed concentrations above 150mM–175mM, and that the buffer concentration in the reaction medium should not be less than 50mM–75mM. Increasing the number of reactors from 4 to 8 or 10 leads to higher productivity of 6‐APA, and a moderate recycle in the first couple of reactors diminishes the sharp decrease in pH which will be found in a straight plug flow reactor operation of the equipment. Higher pumping costs and lower productivity are unavoidable drawbacks of an operation mode where the separation costs for the product mixture are desired to be low.
Mixing characteristics and startup of anaerobic downflow stationary fixed film (DSFF) reactors
Authors: Samson Rejean , van den Berg L. (Bert) , Kennedy Kevin J. 
Published: December 2004

AbstractTests to determine the mixing characteristics of the anaerobic downflow stationary fixed film (DSFF) reactor during startup showed that mixing characteristics affected performance. Different mixing profiles were obtained by keeping the same flow distribution system and by varying the number of clay channels (1, 4, and 25) in the DSFF reactors (2–32 L). Results with a clean bed reactor indicated a plug flow pattern with a relatively large extent of dispersion. Recirculation dramatically improved the mixing and the residence time distribution (RTD) changed to that of the completely mixed type. Multiple‐channel reactors exhibited a dead space of ca. 12% of the total volume, likely a result of a less than optimally designed flow distributor. A startup period of 90 days was necessary to achieve a maximum loading rate of between 10 and 15 kg COD/m3 day, a volumetric methane production rate of up to 3 m3 (STP)/m3 day and a COD reduction efficiency of up to 90%. For the first 50 days of operation, the difference in achievable volumetric loading rate and volumetric methane production rate was only related to the surface‐to‐volume ratio of the reactors and was not affected by the number of channels present. After 90 days, the bacterial growth on the support material was sufficient to dramatically increase the amount of dead space in the reactors, especially in multiple‐channel reactors (up to 55% of their volume). As a result, the performance of these reactors deteriorated and overloading characteristics were observed. Other results showed that biogas production alone was not sufficient to improve reactor mixing and that little or no shortcircuiting or channelling occurred. Furthermore, the nonmethanogenic bacterial activity in the liquid phase was not affected by the degree of mixing but acetoclastic methanogenic and hydrogenophilic methanogenic activity in the liquid phase were reduced as the fluid flow pattern in the reactor improved.
Stability and performance of mesophilic anaerobic fixed‐film reactors during organic overloading
Authors: Kennedy K. J. , Muzar M. , Copp G. H. 
Published: December 2004

AbstractThe stability of downflow stationary fixed‐film (DSFF) reactors was evaluated under extreme organic shock loads. Reactors could handle five‐ to sevenfold increases in organic loading and recover to normal performance in a relatively short period of time (usually 24–72 h) during treatment of well‐buffered sucrose and acetic acid wastewater at 27 and 35°C. Overloading was characterized by elevated volatile‐acid concentrations, decreased reactor pH, and excess biofilm sloughing. Reactors could not cope with extreme organic shocks during treatment of poorly buffered sucrose wastewater. The pH of the mixed liquor was observed to be a more important factor than the volatile‐acid concentration in determining whether DSFF reactors would recover in a reasonable period of time.
State analysis of fermentation using a mass spectrometer with membrane probe
Authors: Heinzle E. , Kramer H. , Dunn I. J. 
Published: December 2004

AbstractA new method of continuous process analysis in fermentation using a mass spectrometer (MS) membrane probe is described. A number of samples from industrial fermentations were analyzed for the occurrence of volatiles detectable with a silicone membrane probe connected to a quadrupole MS. In all fermentations, characteristic spectra were observed which were found to change systematically during the batch process. Factor analysis was used to treat the data. The factor scores were compared with the actual product concentrations (antibiotics, toxins, etc.), which were measured using other analytical methods and were found to correlate with them. On‐line analysis was also carried out on a fermentation with an MS and an Apple II microcomputer. Direct monitoring of products, which are not directly measurable with the membrane MS probe requires a new calibration each time conditions such as medium composition are changed.
Kinetics of condensation of glucose into maltose and isomaltose in hydrolysis of starch by glucoamylase
Authors: Shiraishi Fumihide , Kawakami Koei , Kusunoki Koichiro 
Published: December 2004

AbstractKinetics of the condensation of glucose into maltose and isomaltose in the hydrolysis of starch by two types of glucoamylase (from Aspergillus niger and Rhizopus niveus) was studied both experimentally and theoretically. A kinetic model for the hydrolysis of starch by glucoamylase from A. niger was proposed. In this model the reversible hydrolysis of maltose and isomaltose and the kinetic parameters change were taken into consideration. Calculated values agreed approximately with the experimental results, and this simple kinetic model was found to have practical use. The rate of condensation of glucose into isomaltose by enzyme from A. niger was about three times larger than that by enzyme from R. niveus. At a higher initial concentration of starch a large amount of isomaltose was reversed, and the glucose yield was reduced significantly after very long reaction times.
Optimizing alcohol production from whey using computer technology
Authors: Zertuche Leticia , Zall Robert R. 
Published: December 2004

AbstractThis study was undertaken with the major goal of optimizing the ethanol production from whey using computer technology. To reach this goal, a mathematical model that would describe the fermentation and that could be used for the optimization was developed. Kluyveromyces fragilis was the microorganism used to ferment the lactose in the whey into ethanol. Preliminary studies showed that K. fragilis produced about 90% of the theoretical ethanol yield when grown in whey‐complemented media. However, when this yeast is grown in nonsupplemented whey media, it does not produce more than 32% of that yield. Comparative batch fermentations of lactose and whey‐complemented media showed that whey possibly contains enhancing components for yeast growth and ethanol production. To obtain the mathematical model, the one‐to‐one effect of the process variables (lactose and yeast extract concentrations, air flowrate, pH, and dilution rate) on the ethanol production were first investigated. Experiments on the pH effect showed that a decrease in pH from 7 to 4 produced an increase in ethanol concentration from 16.5 to 26.5 g/L (50 g/L initial lactose). The results obtained from modeling of the continuous fermentation using the previously listed variables showed that air flowrate, pH, and dilution rate were the process variables that most influence the production of ethanol.
Covalent coupling of microorganisms to a cellulosic support
Authors: Okita W. Blair , Bonham D. Bivings , Gainer John L. 
Published: December 2004

AbstractMethods for the covalent coupling of microorganisms to a solid support were investigated. Both bacteria and yeast were attached to cellulose particles using cyanuric chloride as the coupling agent, although different experimental procedures were needed for the two types of microbes. This general technique for whole‐cell immobilization offers an advantage over entrapment methods in that the cells are attached to the outer surface of the solid, thus eliminating the resistance of a gel to the transfer of nutrients and products. There are also indications that such immobilized cells show high productivities.
Calculation of mean cell residence time for unsteady‐state activated sludge systems
Authors: Vaccari David A. , Fagedes Tom , Longtin Jon 
Published: December 2004

AbstractA formulation to calculate the mean cell residence time (MCRT or sludge age) of unsteady‐state activated sludge systems is presented. The formulation was studied by applying it to data generated by computer simulation and to data obtained from an actual wastewater treatment plant. The computer simulation study allowed the effects of step and pulse changes in biochemical oxygen demand (BOD) loading, and step changes in a control variable, waste sludge flow rate, to be studied independently of each other and of other disturbances. The unsteady‐state MCRT formulation (herein called the dynamic sludge age, or DSA) was found to be an improvement over the traditional steady‐state calculation, both for process control, and for research into activated sludge dynamics.
Purification of glucagon by subunit exchange chromatography
Authors: Carrea Giacomo , Pasta Piero , Antonini Eraldo 
Published: December 2004

AbstractGlucagon was immobilized onto Sepharose matrices activated with CNBr or tresyl chloride, as a function of several parameters including pH of coupling, concentration of added polypeptide, and presence or absence of urea. The hormone was linked to the matrix through a single point per molecule, namely, the ε ‐amino group of Lys12 when the coupling was carried out at alkaline pH, or the imidazole group of His1 when the coupling was carried out at acidic pH. Glucagon immobilized at alkaline pH interacted specifically with soluble glucogon. The extent of self‐association was similar to that of free glucagon, which exists in solution in a monomer–trimer equilibrium whose association constant is highly dependent on the characteristics of the buffer (pH, ionic strength, and nature of anions). The immobilized hormone proved to be suitable for the purification of the free one from a pancreatic extract. After a preliminary treatment with charcoal‐dextran, the extract was percolated on a glucagon–Sepharose column under associating conditions (high concentrations of salting out anions and alkaline pH) and then, following a washing to remove extraneous compounds, the specifically bound hormone was eluted under dissociating conditions (low ionic strength). The subunit exchange chromatography of the extract gave a ca. 90% pure product. The overall recovery of the process was ca. 66%. The leakage of immobilized hormone was 40% in the case of CNBr activation of Sepharose and 15% in the case of tresyl chloride activation, after an eight‐day treatment under working conditions.
On‐line estimation of mycelial cell mass concentrations with a computer‐interfaced filtration probe
Authors: Thomas Douglas C. , Chittur Venkatesh K. , Cagney Judy W. , Lim Henry C. 
Published: December 2004

AbstractThis article deals with the design and operation of a filtration probe for estimating cell concentrations in fermentations involving mycelial organisms such as Penicillium chrysogenum. This device, a much improved version of one developed previously, is placed directly into the fermentor and measures the filtration properties of the fermentation broth, which are correlated to the cell concentration. The probe is connected to a computer system which enables on‐line estimation of the cell concentration. Fiber‐optic light guides are used in combination with a pair of light sources and receivers to detect the relative position of the filter‐cake–fermentation‐broth interface. The lower sensor in the filtration tube enables reliable estimation of cell mass upto about 20 g/L (dry wt), while the upper sensor yields useful measurement of the filtration properties upto a concentration of about 40 g/L (dry wt) and appears to have the potential to go even higher. Major advantages of this probe system are the ease of measurement and the on‐line ability to measure very frequently, due to its nondestructive mode of operation. Thus, the probe obviates the need for manual sampling and reduces the risk of contaminating the culture. But, more significantly, it enables one to implement on‐line schemes including feedback control.
Optimization of the activity in porous media of proton‐generating immobilized enzymatic reactions by weak acid facilitation
Authors: Ruckenstein E. , Rajora P. 
Published: December 2004

AbstractIn addition to the role of maintaining the pH, buffers can also facilitate the transport of H+ ions in acid‐generating systems. The role of this facilitation in proton transport in porous pellets on acid‐generating immobilized enzymic reactions is examined. The activity in these systems can be maximized by a proper control of facilitation, which involves the determination of the appropriate variables out of (1) the concentration of the weak acid, (2) the pH of the medium, (3) the bulk substrate concentration, and (4) the type of weak acid. Since the intrinsic activity (IA) of the immobilized enzyme is such that it exhibits an optimum with respect to the pH, a partial (optimal) removal of diffusional limitation by facilitation maximizes the activity when the bulk pH is larger than this optimum pH. A complete removal of diffusional limitations, however, maximizes the activity when the bulk pH is less than or equal to the above optimum pH. The control of the diffusional resistance can be achieved by controlling the extent of facilitation, hence by adjusting the parameters mentioned above. Computations have been carried out to examine the effect of each of these parameters on the activity of the immobilized enzyme. It is found that when the bulk pH is less than or equal to the optimum pH of the intrinsic activity of the immobilized enzyme, there exists a lower limit on the amount of weak acid required to maximize the activity. However, an optimum amount of weak acid is required to maximize the activity when the bulk pH is higher than that optimum pH. For a given activity the amount of weak acid is minimal if the pK of the weak acid is close to the bulk pH. The effect of coupling between the proton and substrate transport on activity control is also examined and the effect of geometry on activity is evaluated for spherical, cylindrical, and flat‐plate configurations.
A new technique for the production of immobilized biocatalyst in large quantities
Authors: Hulst A. C. , Tramper J. , van't Riet K. , Westerbeek J. M. M. 
Published: December 2004

AbstractA new technique is presented for the production of immobilized biocatalysts in large quantities. It consists of breaking up a jet of the biocatalyst/presupport mixture in uniform droplets by means of a resonance technique. Entrapment of yeast and plant cells in calcium alginate has been used as the model. The production capacity of the nozzles used (0.5, 0.8, and 1.1 mm exit diameters) is two orders of magnitude larger than the production capacity of the conventional techniques (maximum capacity with a 1.1‐mm nozzle diameter is 24 L/h). Depending on frequency, nozzle diameter, and volumetric flow rate, the bead size varies between 1 and 2 mm, with standard deviations of 3‐5% for yeast immobilization and 10‐15% for plant cells. The deactivation of both yeast and plant cells is small and comparable to that found in the corresponding conventional procedures.
A new batch calorimeter for aerobic growth studies
Authors: Dermoun Z. , Boussand R. , Cotten D. , Belaich J. P. 
Published: December 2004

AbstractA microcalorimeter for aerobic growth studies, derived from a Tian Calvet differential apparatus, was successfully constructed. The calorimetric vessel was a short cylinder, which permitted a good exchange between the surface area and the gas phase. The time constant of the calorimeter was 3.6 min and the sensitivity 234 V/W. The thermochemical aspect of the aerobic growth of Escherichia coli on succinate, acetate, and glucose was investigated. This analysis revealed that the contribution of biosynthetic reactions varied with the substrate used and strongly influenced the heat evolution. The experimental metabolic enthalpy change was in good agreement with the predicted value for succinate and glucose growth. To explain the discrepancy between the two values observed for acetate growth we suggest that acetate metabolism may generate a by‐product which was not further oxidized.
Enzymatic hydrolysis of cellulose in aqueous two‐phase systems. II. Semicontinuous conversion of a model substrate, solka floc BW 200
Authors: Tjerneld Folke , Persson Ingrid , Albertsson Per‐Åke , Hahn‐Hägerdal Bärbel 
Published: December 2004

AbstractA model substrate, Solka Floc BW 200, was semicontinuously hydrolyzed in an aqueous two‐phase system based on crude dextran and polyethylene glycol over a period of more than 450 h. With an initial concentration of 75 g/L and intermittent addition of cellulose an average concentration of 50 g/L sugar was semicontinuously produced at dilution rates of 0.006–0.012 h−1. The conversion of substrate varied between 49 and 66%. The enzyme consumption measured as FPU/g reducing sugar (RS) produced could be reduced by a factor two when compared to a batch process since, in the aqueous two phase system investigated, the enzyme could be recycled two times.
Effects of aromatic compounds on hemicellulose‐degrading enzymes in Aspergillus japonicus
Authors: Sharma A. , Milstein O. , Vered Y. , Gressel J. , Flowers H. M. 
Published: December 2004

AbstractAspergillus japonicus was grown in the presence of various aromatic compounds at 0.1 and 1 mg/mL, and extracellular xylanase and arabanase activities were measured. Some of the aromatic compounds tested, especially at the higher concentration, suppressed the appearance of hemicellulase activities, expressed as xylanase or arabanase. Vanillin at 1 mg/mL in the presence of either xylan or araban completely suppressed growth, and guaiacol and p‐coumaric acid markedly inhibited the growth of A. japonicus. The effects of the aromatic compounds on the activity of crude enzyme preparations were also ascertained. In vitro arabanase activity was affected more than xylanase activity.
Immobilized live cell reactor dynamics following dilution rate shift to growth conditions: Cell synchrony effects
Authors: Bailey Kevin M. , Venkatasubramanian K. , Karkare Subhash B. 
Published: December 2004

AbstractNutrient deprivation was used to synchronize an immobilized live cell culture of Acetobacter suboxydans. The substrate supply was increased by a step change in the dilution rate to the reactor. Oscillations in cell, substrate, and product concentrations were observed. A population balance model was developed to explain the observed reactor dynamics. Simulation results based on the model were used to substantiate the premise that cell synchrony is the likely phenomenon responsible for the observed oscillations. The implications of cell synchrony in immobilized cell systems are discussed briefly.
Semicontinuous affinity chromatography separations
Authors: McCoy B. J. 
Published: December 2004

AbstractThe semicontinuous operation of affinity chromatography columns charged and eluted alternately is studied mathematically. A strongly nonlinear adsorption equilibrium relation is utilized to examine the periodic mode of adsorption and desorption. The governing differential equations are solved by the method of characteristics. The time interval between desorption and adsorption periods is estimated, and implications for separations are discussed to show the advantages of semicontinuous cyclic operation.
Influence of H2 stripping on methane production in conventional digesters
Authors: Poels J. , van Assche P. , Verstraete W. 
Published: December 2004

AbstractHydrogen is a central metabolite in the methanization process. In this study the partial pressure of hydrogen in the gas phase of laboratory manure digesters was monitored over extensive periods of time and found to vary between 50 and 100.10−6 atm. By sparging the gas phase of the digester through an auxiliary reactor, hydrogenotrophic methanogens were allowed to develop at the expense of hydrogen and carbon dioxide present in the biogas, independently of the liquid or cell residence time in the main reactor. By scrubbing ca. 100 volumes of biogas per liter reactor per day through an auxiliary reactor, hydrogen concentration could be decreased maximally 25%. This resulted in an increase in the gas production rate of the main digester of ca. 10% and a concomitant improved removal of volatile fatty acids from the mixed liquor. The results obtained indicate that considerable stripping of hydrogen from the digester could be achieved at acceptable energy expenditure. However, the microbial removal of the hydrogen at these low concentrations is extremely slow and limits the applicability of this approach.