bluuebunny/crossref_metadata_2025_split huggingface dataset:
The electrochemical regeneration of NAD+ revisited
Authors: Laval Jean‐Marc , Bourdillon Christian , Moiroux Jacques 
Published: December 2004

AbstractAn actual yield of 99.97% (i.e., 3000 potential regenerating cycles) has been obtained for the electrochemical regeneration of NAD+. The deactivation of the coenzyme is not related to the number of cycles; it is only time dependent. For biotechnological applications, these results show that electrochemical regeneration can compete with enzymatic regeneration for selective oxidation by dehydrogenases.
Biomass retention and performance of anaerobic fixed‐film reactors treating acetic acid wastewater
Authors: Hamoda M. F. , Kennedy K. J. 
Published: December 2004

AbstractAn acetic‐acid‐based synthetic wastewater of different organic concentrations was successfully treated at 35°C in anaerobic downflow fixed‐film reactors operated at high organic loading rates and short hydraulic retention times (HRTs). Substrate removal and methane production rates close to theoretical values of complete volumetric chemical oxygen demand (COD) removal and maximum methane conversion were obtained. A high concentration of biofilm biomass was retained in the reactor. Steady‐state biofilm concentration increased with increased organic loading rate and decreased HRTs, reaching a maximum of 8.3 kg VFS/m3 at a loading rate of 17 kg COD/m3 day. Biofilm substrate utilization rates of up to 1.6 kg COD/kg VFS day were achieved. Soluble COD utilization rates at various COD concentrations can be described by half‐order reaction kinetics.
Adaptive steady‐state optimization of biomass productivity in continuous fermentors
Authors: Harmon Jeff , Svoronos Spyros A. , Lyberatos Gerasimos 
Published: December 2004

AbstractAn adaptive steady‐state optimization algorithm is presented and applied to the problem of optimizing the production of biomass in continuous fermentation processes. The algorithm requires no modeling information but is based on an on‐line identified linear model, locates the optimum dilution rate, and maintains the chemostat at its optimum operating condition at all times. The behavior of the algorithm is tested against a dynamic model of a chemostat that incorporates metabolic time delay, and it is shown that large disturbances in the subtrate feed concentration and the specific growth rate, causing a shift in the optimum, are handled well. The developed algorithm is also used to drive a methylotroph single‐cell production process to its optimum.
Factors affecting biomass attachment during startup and operation of anaerobic fluidized beds
Authors: Stronach Sandra M. , Diaz‐Baez Maria C. , Rudd Thomasine , Lester John N. 
Published: December 2004

AbstractThree anaerobic fluidized bed reactors at 37°C were utilized to observe the effects of startup and operational procedures on biomass attachment. Using a meat‐based synthetic waste and stepped‐loading regime, the influences of synthetic polymer addition and maintenance of anaerobiosis during startup were investigated. Subsequently, increasing bed expansions were applied to assess shear effects. Synthetic polymer addition enhanced biomass retention but did not improve process performance. Maintenance of a reduced environment ameliorated fluctuating process parameters during start up and aided biomass retention and substrate removal. A bed expansion of 5% was detrimental to biomass attachment and COD removal but system stability was maintained at expansions between 10% and 30%. Startup was achieved in 56 days. Anaerobiosis appeared to enhance the initial evolution of a stable, well‐adapted microbial population, whereas polymer addition interfered with this. Moderate bed expansions had negligible effects on attachment and performance.
Oxygen transfer to mycelial fermentation broths in an airlift fermentor
Authors: Moo‐Young Murray , Halard Benoit , Allen D. Grant , Burrell Robert , Kawase Yoshinori 
Published: December 2004

AbstractOxygen transfer rates and gas holdups were measured in mycelial fermentation broths of Chaetomium cellulolyticum and Neurospora sitophila, each cultured in a 1300‐L pilot‐plant‐scale airlift fermentor. These cultures exhibited highly non‐Newtonian flow behavior coupled with a substantial decrease in oxygen transfer rates. The volumetric mass transfer coefficients in these cultures were found to be 65–70% lower than those in water. The data were compared with the available correlations obtained for simulated fermentation broths. In general, the data for C. cellulolyticum are in satisfactory agreement with the correlations for the model media but the data for N. sitophila are higher than that predicted by the correlations. Model media based correlations are found to be applicable to the fermentation processes if the culture medium does not possess a high yield stress.
Anaerobic digestion of wood ethanol stillage using upflow anaerobic sludge blanket reactor
Authors: Callander I. J. , Clark T. A. , McFarlane P. N. 
Published: December 2004

AbstractThe anaerobic digestion of wood ethanol stillage in a UASB reactor was studied. At organic loading rates be low 16 kg COD/m3 day the reactor performed effectively, achieving soluble COD and BOD removals in excess of 86 and 93%, respectively. Removal of color averaged 40%. At a loading rate of 16 kg COD/m3 day the methane yield was 0.302 L CH4 (STP)/g COD removed, and the observed cell yield was 0.112 g VSS/g COD removed. Operation of the reactor at higher loading rates was unsuccessful. Nitrogen, phosphorus, and alkalinity were supplemented. No additions of the essential trace elements Fe, Co, and Ni were required.
Economic assessment of plant cell culture for the production of ajmalicine
Authors: Drapeau D. , Blanch H. W. , Wilke C. R. 
Published: December 2004

AbstractCost estimates have been prepared for commercial‐scale production of ajmalicine‐rich Catnaranthus roseus biomass using plant cell culture. At the current state of the technology the cost would be approximately $7.30/lb dry biomass ($3215/kg ajmalicine). Naturally‐grown C. roseus roots have a 50% lower ajmalicine concentration but would cost only ca. $0.70/lb ($619/kg ajmalicine). The principal reason for the high cost of the plant cell culture route is not the slow specific growth rate (0.35 day−1), but rather the slow specific product accumulation rate (0.26 mg/g day). This rate will have to be increased by a factor of 40 to make the process competitive.
Concentration multiplicity in a draft tube fluidized‐bed bioreactor involving two limiting substrates
Authors: Tong C. C. , Fan Liang‐Shih 
Published: December 2004

AbstractConcentration multiplicity in a two‐phase or three‐phase draft tube fluidized‐bed bioreactor containing biofloc particles is studied. The kinetics of biological reactions considered involve two limiting substrates. The necessary and sufficient conditions for concentration multiplicity in both the biofilm and bioreactor are examined in terms of effectiveness factor, inlet and bulk concentration of substrates, and liquid flow rate. Hysteresis behavior in both the biofilm and bioreactor and multiplicity of concentration profiles in the biofilm are also discussed.
Biomass photochemistry: XI. Photochemical pretreatment of cellulose and its fungal degradation
Authors: Durán Nelson , Rodríguez Jaime , Gómez Edgardo , Campos Victoriano , Baeza Jaime 
Published: December 2004

AbstractIn order to study the single‐cell proteins and cellulase production, fungal degradation of α‐cellulose was tested. Photochemical pretreatment of α‐cellulose at λ > 254 nm increases by over 100% the cellulase production by Chrysonilia sitophila (TFB strain). This is reflected in a larger production of soluble proteins in the filtrate with higher cellulase activity when compared with unirradiated cellulose. Single‐cell protein production (insoluble proteins) was also improved after preirradiation of cellulose or even on rice hull as the only carbon source after inoculation with the spore of C. sitophila. This pretreatment is a valuable method for increasing the digestibility of lignocellulosic materials.
Modeling and analysis of elution stage of biospecific adsorption in finite bath
Authors: Arve B. H. , Liapis A. I. 
Published: December 2004

AbstractA model is developed and used to predict the dynamic behavior of the elution stage of biospecific adsorption (affinity chromatography) in a finite bath. Both nonselective and selective elution of monovalent adsorbates is considered. The model expressions account for film and pore diffusion resistances for the adsorbate(s) and the eluent, and various rate expressions for the desorption of the adsorbate from the adsorbate–ligand complex are constructed and studied. The results indicate that the duration of the elution stage depends significantly on the Sherwood number of the adsorbate and the rate of the interaction step between the ligand and the adsorbate relative to the diffusion of the adsorbate in the pore during elution. In nonselective elution, when the value of the effective pore diffusivity of the eluent is significantly larger than that of the adsorbate, the results suggest that it would be advantageous to use an initial eluent concentration in the finite bath that is only slightly higher than the critical eluent concentration in order to minimize the risk of product and ligand damage. In selective elution the amount of adsorbate recovered in the elution stage is greatly influenced by the initial concentration of the eluent and the equilibrium dissociation constants of the adsorbate–ligand and adsorbate–eluent complexes.
Kinetics of α‐amylase synthesis from Bacillus amyloliquefaciens
Authors: Yoo Young J. , Cadman Theodore W. , Hong Juan , Hatch Randolph T. 
Published: December 2004

AbstractThe microbial production of α‐amylase from Bacillus amyloliquefaciens was investigated. The microorganism was grown using media containing glucose or maltose at 37°C and under aerobic conditions in a 16‐L fermentor. The α‐amylase synthesis from maltose was not found to be inducible but was found to be subject to catabolite repression. The maltose uptake rate was observed to be the rate‐limiting step compared to the conversion rate of maltose to glucose by intracellular α‐glucosidase. The α‐amylase activity achieved with maltose as a substrate was higher than that achieved with glucose. A slower growth rate and a higher cell density were obtained with maltose. The enzyme production pattern depended upon the nutrient composition of the medium.
Improved performance of intensive semicontinuous cultures of Scenedesmus by biomass recirculation
Authors: de la Noüe J. , Ní Eidhin D. 
Published: December 2004

AbstractThe microscopic green alga, Scenedesmus obliquus, was used in a semicontinuous culture system for the tertiary treatment of urban wastewater, with the simultaneous production of usable biomass. Partial biomass recycling was used to increase the productivity of the system by overcoming the limits imposed by the low maximal growth rate of the alga. The biomass to be recycled was collected by simple gravity settling of the removed culture.The culture system was operated at different dilution rates and its productivity measured at each rate. An evaluation of the crude nutrient composition of the algae produced at each dilution rate was also carried out.The system was found to operate stably at dilution rates of up to 0.8 day−1 which represents a 20% net increase over the maximum dilution rate allowed under the same conditions in a system without recirculation. The composition of the biomass produced varied little over a range of dilution rates, which may be of relevance to its projected end‐use.The study indicated that such a system can exploit available light to the full and should be of particular value for the treatment of low‐strength wastes such as we employed.
Discovery of a human erythroid differentiation factor (EDF) and its large‐scale production
Authors: Tsuji T. , Eto Y. , Takano S. , Takezawa M. , Yokogawa Y. , Shibai H. 
Published: December 2004

AbstractA novel human protein exhibiting erythroid differentiation activity was discovered in the culture fluids of phorbol ester‐stimulated human cells. The differentiation assay system involving Friend virus‐derived mouse leukemia cells was used. THP‐1 cells of myelomonocytic origin were typical producers. 4β‐Phorbol 12‐myristate 13‐acetate (PMA) was essential for inducible excretion of the erythroid differentiation factor (EDF). The factor was stable toward heat and pH (acidic or alkaline) but lost its activity on pronase treatment, which suggested its proteinous nature. After an optimization of the condition, production of EDF was performed on a 200‐L scale for purification of the protein.
Comparison of free and immobilized Pichia pastoris cells for conversion of ethanol to acetaldehyde
Authors: Duff Sheldon J. B. , Murray William D. 
Published: December 2004

AbstractFree and immobilized cells of Pichia pastoris were used to convert ethanol to acetaldehyde in small‐scale batch reactors. Immobilized cells were less active than free cells (Vmax free = 7.81 g/L h, Vmax immobilized = 3.17 g/L h) due to a number of factors including end product inhibition and diffusional limitations. Immobilized cells were more resistant to heat denaturation both in the presence and absence of ethanol. Immobilized cells retained more of their activity during repeated batch cycles than did free cells.
Continuous fractionation of human plasma proteins by precipitation from the suspension of the recycling stream
Authors: Chang Chong E. 
Published: December 2004

AbstractThe conventional cold‐ethanol batch fractionation method of human plasma is converted to an automatically controlled continuous fractionation process. The selected protein fractions are precipitated by mixing in the recycled product stream of the suspension. Compared to the batch process, the continuous fractionation process generates less coprecipitation and less spontaneous nucleation, allowing efficient centrifugation of precipitates, and the yield and purity of albumin in the final fraction is significantly increased.
Biochemical limits to microbial growth yields: An analysis of mixed substrate utilization
Authors: Gommers P. J. F. , van Schie B. J. , van Dijken J. P. , Kuenen J. G. 
Published: December 2004

AbstractA theoretical analysis has been made of carbon conversion efficiency during heterotrophic microbial growth. The expectation was that the maximal growth yield occurs when all the substrate is assimilated and the net flow of carbon through dissimilation is zero. This, however, is not identical to a 100% carbon conversion, since assimilatory pathways lead to a net production of CO2. It can be shown that the amount of CO2 produced by way of assimilatory processes is dependent upon the nature of the carbon source, but independent of its degree of reduction and varies between 12 and 29% of the substrate carbon. An analysis of published yield data reveals that nearly complete assimilation can occur during growth on substrates with a high energy content. This holds for substrates with a heat of combustion of ca. 550 kJ/mol C, or a degree of reduction higher than 5 (e.g. ethane, ethanol, and methanol). Complete assimilation can also be achieved on substrates with a lower energy content, provided that an auxiliary energy source is present that cannot be used as a carbon source. This is evident from the cell yields reported for Candida utilis grown on glucose plus formate and for Thiobacillus versutus grown on acetate plus thiosulfate. This evaluation of the carbon conversion efficiency during assimilation also made it possible to compare the energy content of the auxiliary energy substrate added with the quantity of the carbon source it had replaced. It will be shown that utilization of the auxiliary energy source may lead to extreme changes in the efficiency of dissimilatory processes.
Modelling ethanol and secondary inhibitions of ethanol fermentation in a multistage reactor
Authors: Chattaway Thomas , Goma Gérard , Renaud Pierre‐Yves 
Published: December 2004

AbstractA kinetic model of ethanol fermentation conducted under a variety of conditions in a continuous four‐stage reactor is proposed. The expressions for specific growth and product formation rates are:

Parameters were identified by nonlinear programming and shown to fit data correctly for steady states of seven different experiments. The product inhibition constants were of 27 and 84 g/L, respectively. Secondary inhibitions were represented by the linear biomass term. The proposed model gave a better description of phenomena than one which only took ethanol inhibition into account. The same model also fitted batch fermentation data, with only some parameters altering significantly. The use of this model for on‐line purposes is discussed.
An immobilized hydrogenase from Alcaligenes eutrophus H‐16
Authors: Deloggio Theodore J. , Graves David J. 
Published: December 2004

AbstractAlcaligenes Eutrophus H‐16 was grown in continuous culture under conditions which induced hydrogenase production. The hydrogenase enzyme was extracted, partially purified and immobilized on porous glass. This enzyme was then studied both in solution and in immobilized form as a possible candidate for a number of industrial applications. It proved to have a stability (storage and operational) which was highly temperature dependent. Temperatures near freezing caused the enzyme to retain its activity for long periods of time. Although its kinetics were more favorable at elevated temperatures of up to 40°C, the loss of stability outweighed this gain substantially. The effects of buffer type and pH on enzyme activity were also studied. This enzyme has only a modest sensitivity to destruction by oxygen during storage, in contrast to hydrogenases produced by several other microorganisms.
Effects of microorganisms on effective oxygen diffusion coefficients and solubilities in fermentation media
Authors: Ho Chester S. , Ju Lu‐Kwang 
Published: December 2004

AbstractEffective oxygen diffusion coefficients and solubilities were measured for submerged cultures of Saccharomyces cerevisiae, Escherichia coli, and Penicillium chrysogenum. Both effective oxygen diffusion coefficients and solubilities were found to decrease with increasing cell concentrations in the fermentation media. Comparison of the experimental results of effective oxygen diffusion coefficients in fermentation media with values theoretically predicted on the assumption of unpenetrable microbial cells indicates that oxygen molecules diffuse through the cells during the diffusion process. Within the cell concentration range of typical submerged fermentations, the effective oxygen diffusion coefficient of the fermentation media can be described as De = A1f + A2f2. In this equation, fis the cell volume fraction and both A1 and A2 are functions of the shape of the cells and the ratio of effective oxygen diffusion coefficient in microbial cells to that in the medium.
Transient response simulations of recombinant microbial populations
Authors: Peretti S. W. , Bailey J. E. 
Published: December 2004

AbstractAn asynchronous bacterial population has been approximated using a finite number of “computer” cells, each based on a complex single‐cell model for Escherichia coli. This formulation correctly simulates the transient responses of protein and total cell mass synthesis rate to the sudden increase in the concentration of limiting energy source in the growth medium. Experimentally observed responses of rRNA and mRNA synthesis rates to growth rate shifts are qualitatively mirrored by the model. Simulation trends following those of a rel− mutant suggest that model modifications are needed to describe the dynamics of the stringent response. Simulations of the responses of recombinant populations to plasmid amplification or plasmid promoter induction also result in behavior similar to that determined experimentally. The calculated responses for recombinant populations subjected to constant promoter induction or cyclic induction‐noninduction lead to the conclusion that inducible systems give greater productivity than those with fixed promoter strength. This formulation may be utilized as a basis for exploring other aspects of recombinant population dynamics.
Nature and significance of oscillatory behavior during solvent production by Clostridium acetobutylicum in continuous culture
Authors: Clarke Kim G. , Hansford Geoffrey S. , Jones David T. 
Published: December 2004

AbstractThe concurrent production of acids and solvents and the production of acetone during continuous culture in a product‐limited chemostat indicated that the culture contained a mixture of acid‐ and solvent‐producing cells. Periodic oscillations in the yield of end products and the specific growth rate of the culture were ob served during undisturbed continuous culture at a constant dilution rate. The increased specific growth rate was associated with an increased acid yield and an increase in the rate of cell division and the proportion of short rods. The decreased specific growth rate was as sociated with an increase in the solvent yield and a decrease in the rate of cell division, resulting in the production of elongated rods. It is proposed that the oscillatory behavior observed during continuous culture is an inherent characteristic related to the shift from primary to secondary metabolism. A major consequence of the oscillation of the specific rates of growth and division in cultures containing acid‐ and solvent‐producing cells is that it precludes the attainment of a true steady state during continuous culture.
Properties of invertase immobilized on the poly(ethylene‐co‐vinyl alcohol) hollow fiber membrane
Authors: Shiomi Tomoo , Tohyama Masao , Satoh Mikitoshi , Miya Masamitsu , Imai Kiyokazu 
Published: December 2004

AbstractInvertase was ionically immobilized on the poly(ethylene‐co‐vinyl alcohol) hollow fiber inside surface, which was aminoacetalized with 2‐dimethylaminoacetaldehyde dimethyl acetal. Immobilization and enzyme reaction were carried out by letting the respective solutions pass or circulate through the inside of the hollow fiber, and the activity of invertase was determined by the amount of glucose produced enzymatically from sucrose. Immobilization conditions were examined with respect to the enzyme concentration and to the time, and consequently the preferable conditions at room temperature were found to be 5 μg/mL of enzyme concentration and 4 h of immobilization time. Under those conditions the immobilization yield and the ratio of the activity of the immobilized invertase to that of the native one were 89 and 80%, respectively. For both repeating and continuous usages, the activity fell to ca. 60% of the initial activity in the early stage and after that almost kept that value. The apparent Michaelis constant K for the immobilized invertase decreased with increasing the flow rate of the substrate solution, to be close to the value for the native one. Furthermore, the possibility of the separation of the enzymatically formed glucose from the reaction mixture through the hollow fiber membrane was preliminarily examined.