bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of acetate, propionate and butyrate removal in the treatment of a semi‐synthetic landfill leachate on anaerobic filter
Authors: Gourdon R. , Comel C. , Vermande P. , Véron J. 
Published: May 2005

AbstractThe kinetics of acetate, propionate, and butyrate removal was studied in conditions of leachate treatment in a plug flow anaerobic fixed‐film reactor made of a sequence of seven perfectly mixed compartments. An original experimental procedure was followed under sequential feeding conditions so as to maintain the Bacteriol biomass in a quasi‐steady state all along the study. With an appropriate computer program based on the least squares method, the apparent kinetic parameters of VFA removal were calculated within concentration ranges below the levels of salt inhibition. The models proposed are based on simple theoretical considerations. For acetate and n‐butyrate removal, the best fits were given by the Michaelis‐Menten equation with respectively: V = 0.49 ± 0.06 g CH3 COOH g−1 biomass h−1and 0.18 ± 0.02 g n‐CH3CH2CH2COOH g−1 biomass h−1 and: Ks = 21.2 ± 0.9 g CH3COOH L−1 liquid phase and 8.2 ± 0.9 g n‐CH3CH2CH2COOH L−1 liquid phase, Iso‐butyrate was produced during n‐butyrate catabolism and the apparent removal rate of (n + iso)‐butyrate considered as a whole was also described by the Michaelis‐Menten equation with V = 0.14 ± 0.02 g(n + iso)‐butyrate g−1 biomass h−1 and Ks = 9.0 ± 1.2 g (n + iso) butyrate L−1 liquid phase. On the other hand in the case of propionate, the best fit was obtained with a first‐order equation with Kspec = (0.88 ± 0.05) 10−2 L liquid phase g−1 biomass h−1. These constants were subsequently used to predict the removal of mixtures of the three major VFAs under study, at various feed concentrations. Three sets of concentrations were tested, and the experimental data were compared to the simulations. This study, together with other experimental observations previously reported, tends to show that under sequential feeding conditions the classical assumption of butyrate β‐oxidation should be rejected. Butyrate seems to be anaerobically decarboxylated, but propionate thus formed inside the biofilm is degraded as soon as its formation proceeds. It was therefore considered that butyrate degradation produces, through propionate intermediate, 1 mole acetate per mole butyrate removed. When propionate or butyrate concentrations were high, the same phenomenon was noted, to a much lower extent, for the degradation of acetate formed inside the biofilm.
Production of human immune interferon by recombinant mammalian cells cultivated on microcarriers
Authors: Smiley A. L. , Hu W‐S. , Wang D. I. C. 
Published: May 2005

AbstractRecombinant Chinese hamster ovary (rCHO) cells were cultivated on microcarriers for the production of human immune (Gamma) interferon. The effect of basal medium, serum, and microcarrier concentration on interferon production was investigated. The specific interferon productivity in the post‐confluent stage was similar to that in the growth stage. Control of the pH results in a significant improvement in the volumetric interferon production. The volumetric production rate of interferon by these rCHO cells did not decrease after one month of cultivation on microcarriers.
The heat generated by yeast cultures with a mixed metabolism in the transition between respiration and fermentation
Authors: von Stockar U. , Birou B. 
Published: May 2005

AbstractThe heat generated by both batch and continuous cultures of the yeast K. fragilis was studied using a modified Bench Scale Calorimeter. Batch cultures were used to measure the heat dissipation rates and the heat yields during fully aerobic and completely anaerobic growth, whereas continuous cultures enabled, in addition, a quantitative study of heat dissipation rates during growth on mixed metabolism. In this case, the extent of fermentation versus respiration could be specified and controlled by varying the degree of oxygen limitation. The heat dissipated per unit biomass formed was highest for fully respirative catabolism and fell continuously to a much lower value typical of anaerobic cultures as the catabolism was shifted increasingly to the fermentative mode. The heat generated per mole of oxygen taken up stayed quite close to the fully aerobic value of 506 kJ mol−1 even when a sizable fraction of the substrate available to catabolism was fermented. If the fraction of respiration in the metabolism is lowered beyond a certain threshold, the ratio of the heat generation to oxygen consumption starts to increase dramatically and finally tends to infinity for fully anaerobic growth. All experimental results were quantitatively analyzed and explained on the basis of a simple model which formally describes the cultures in terms of two parallel “chemical” reactions. In simple cases such as the one presented here, the model enables calculation of the whole stoichiometry of the culture from a single measured heat yield.
A simulation study of a continuous two‐phase dry digestion system
Authors: Mata‐Alvarez Joan 
Published: May 2005

AbstractIn this article a two‐phase system for the continuous digestion of wastes with a high solid content is simulated. The studied parameters are: (1) Recirculation from the methanizer to the hydrolyzer, (2) methanizer/hydrolyzer volume ratio, and (3) hydraulic retention time in the hydrolyzer (HRT). Results show that the recirculation ratio is an important operational factor with a large influence on the biodegradation yield, especially at low HRT. Optimum levels of this parameter are established. Some runs of the program have been carried out to test the stability of the system. This has proved to be very stable, especially at low recirculation ratios. The results also show that volume ratio does not appreciably affect the performance of the system, provided it is over a critical value, dictated by the allowable methanizer load.
NADH and flavin fluorescence responses of starved yeast cultures to substrate additions
Authors: Siano S. A. , Mutharasan R. 
Published: May 2005

AbstractModel experiments were performed with starved yeast (Saccharomyces cerevisiae) cultures in a batch reactor in order to develop a better understanding of NAD(P)H and flavin culture fluorescence. Fluorescence was monitored during aerobic–anaerobic–aerobic transitions and ethanol and glucose substrate addition experiments. Interpretations of the fluorescence responses obtained are provided, with consideration given to redox compartmentation and the formation of ethanol shortly after a glucose addition. An analytical spectrofluorophotometer was interfaced to a personal computer and adapted to measure fluorescence in a bioreactor. This was achieved by the use of quartz fiber‐optic waveguides to convert the right‐angle cuvette geometry of the analytical spectrofluorophotometer to an open‐ended fluorescence probe geometry, resulting in a flexible culture fluorescence apparatus. Features of the apparatus include variable excitation and emission wavelengths, allowing for detection of NAD(P)H or flavin fluorescence, as well as small slit widths, a variable sampling rate, excitation and emission scanning capabilities, and good sensitivity.
Kinetics of the hydrolysis of di‐ and trisaccharides with Aspergillus niger glucoamylases I and II
Authors: Meagher Michael M. , Reilly Peter J. 
Published: May 2005

AbstractNear‐homogeneous forms of glucoamylases I and II, previously purified from an industrial Aspergillus niger preparation, were used to hydrolyze a number of di‐ and trisaccharides linked by α‐D‐glucosidic bonds. Maximum rates and Michaelis constants were obtained at various temperatures and pH values with glucoamylase I for the disaccharides β,α‐trehalose, kojibiose, nigerose, maltose, and isomaltose and the trisaccharides panose and iso‐maltotriose, and with glucoamylase II for maltose, maltotriose, and isomaltotriose. Maximum rates were highest and energies of activation were lowest for maltose, maltotriose, and panose, the only three substrates containing α‐D‐(1, 4)‐glucosidic bonds. Michaelis constants were lowest and standard heats of binding were most negative for maltose and maltotriose. The variation of maximum rates and Michaelis constants with varying pH values suggested that two carboxyl groups were involved in substrate binding.
A mathematical description of recombinant yeast
Authors: Coppella Steven J. , Dhurjati Prasad 
Published: May 2005

AbstractA model was formulated to examine specific experimental data of growth and heterologous product formation with recombinant Saccharomyces cerevisiae while incorporating available literature. The model simulated dry cell weight, glucose, ethanol, dissolved oxygen, human Epidermal Growth Factor (hEGF) production, fraction of recombinant cells, oxygen uptake rate, and carbon dioxide production rate for batch, fed batch, and hollow fiber bioreactor configurations. Nineteen differential equations, 24 analytical equations, and 48 parameters were required. Due to the lack of detailed studies needed for the ADH‐II and the TCA enzyme pool, 8 of the 48 parameters were adjustable. Simulation results are presented for verification of the model which successfully described the observed phenomena for the fermentations of S. cerevisiae strain AB103. 1 pYαEF‐25. Also presented is a statistical analysis of the model's fit and model parameter sensitivity.
Vancomycin partitioning in aqueous two‐phase systems: Effects of pH, salts, and an affinity ligand
Authors: Lee Cheng‐Kang , Sandler Stanley I. 
Published: May 2005

AbstractThe partitioning of vancomycin in polyethylene glycol (PEG)‐dextran and PEG‐phosphate aqueous two‐phase systems was studied at different pHs, at varying concentrations of neutral salts, and with an affinity ligand attached to methoxy polyethylene glycol (MPEG). Vancomycin is found to partition preferentially into the PEG‐rich top phase, and its partition coefficient increases nearly exponentially with the addition of water structure‐making salts, such as sodium sulfate and sodium chloride, but is independent of sodium phosphate concentration. In the PEG‐dextran system the vancomycin partition coefficient increases 3‐fold in acidic and neutral solutions, while in the PEG‐phosphate system it increases about 30‐fold on the addition of the same amount of sodium chloride (1. 5 mol/kg). In basic solution, above its isoelectric point, the vancomycin partition coefficient increases slightly with NaCI concentration in the PEG‐dextran system. We also examined the use of the dipeptide D‐ala‐D‐ala as an affinity ligand on MPEG to extract vancomycin into the PEG‐rich phase. The vancomycin partition coefficient increased almost 7‐fold upon adding the MPEG‐ligand in an amount equal to approximately 3% of the total PEG in the system. Finally, fractionation of the polydisperse phase‐forming polymers in the two‐phase PEG‐dextran system was observed. The effect of this polymer fractionation on the partition coefficient of vancomycin is discussed.
Effects of temperature on cell growth and xanthan production in batch cultures of Xanthomonas campestris
Authors: Shu Chin‐Hang , Yang Shang‐Tian 
Published: May 2005

AbstractBatch xanthan fermentations by Xanthomonas campestris NRRL B‐1459 at various temperatures ranging between 22°C and 35°C were studied. At 24°C or lower, xanthan formation lagged significantly behind cell growth, resembling typical secondary metabolism. However, at 27°C and higher, xanthan biosynthesis followed cell growth from the beginning of the exponential phase and continued into the stationary phase. Cell growth at 35°C was very slow; the specific growth rate was near zero. The specific growth rate had a maximum value of 0.26 h−1 at temperatures between 27°C and 31°C. Cell yield decreased from 0.53 g/g glucose at 22°C to 0.28 g/g glucose at 33°C, whereas xanthan yield increased from 54% at 22°C to 90% at 33°C. The specific xanthan formation rate also increased with increasing temperature. The pyruvate content of xanthan produced at various temperatures ranged between 1.9% and 4.5%, with the maximum occurring between 27°C and 30°C. These results suggest that the optimal temperatures for cell growth are between 24°C and 27°C, whereas those for xanthan formation are between 30°C and 33°C. For single‐stage batch fermentation, the optimal temperature for xanthan fermentation is thus dependent on the design criteria (i. e., fermentation rate, xanthan yield, and gum qualities). However, a two‐stage fermentation process with temperature shift‐up from 27°C to 32°C is suggested to optimize both cell growth and xanthan formation, respectively, at each stage, and thus to improve overall xanthan fermentation.
An ESR study of spin‐labeled silk fibroin membranes and spin‐labeled glucose oxidase immobilized in silk fibroin membranes
Authors: Asakura Tetsuo , Yoshimizu Hiroaki , Kakizaki Mitsuhiro 
Published: May 2005

AbstractThis article describes the characteristics of silk fibroin membranes and glucose oxidase, immobilized in membranes as determined by a variety of physical methods, mainly the spin‐label electron spin resonance (ESR) method. The properties of membranes insolubilized by different methods, i. e., immersion in 80% methanol aqueous solution, uniaxially drawing by placing on a stretcher, and hydration by placing in a desiccator of 96% relative humidity (RH) for 17 h, are compared. The results are also analyzed in relation to ESR spectra of spin‐labeled immobilized glucose oxidase and 4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy as a model of the substrate. It is concluded that the heterogeneous structures of the swollen membranes in water differ locally among membranes insolubilized by different methods, but the immobilized state of the enzyme in such membranes is mostly similar. This is correlated to the fact that the thermal or pH stabilities are essentially same among glucose‐oxidase‐immobilized silk fibroin membranes insolubilized by different methods.
Protease immobilization onto polyacrolein microspheres
Authors: Hayashi Toshio , Ikada Yoshito 
Published: May 2005

AbstractWater‐insoluble proteases were prepared by immobilizing papain and chymotrypsin onto the surface of polyacrolein microspheres with and without oligoglycines as spacer. The activity of immobilized proteases was found to be still high toward small ester substrates, but very low toward casein, a high‐molecular‐weight substrate. The relative activity of the immobilized proteases without spacer decreased gradually with the decreasing surface concentration of the immobilized proteases on the microspheres. On the contrary, the immobilized proteases with oligoglycine spacers gave an almost constant activity for the substrate hydrolysis within the surface concentration region studied and gave a much higher relative activity than those without any spacer. With the longer spacer, the immobilized enzymes showed a higher activity toward casein hydrolysis, whereas there was an optimum length for the spacer when hydrolysis was carried out toward the low‐molecular‐weight substrate. The thermal stability of the immobilized proteases was higher than that of the respective native proteases. The initial enzymatic activity of the immobilized proteases maintained almost unchanged without any elimination and inactivation of proteases, when the batch enzyme reaction was performed repeatedly, indicating the excellent durability.
Microbial control of the production of hydrogen sulfide by sulfate‐reducing bacteria
Authors: Montgomery Anne D. , Mclnerney Michael J. , Sublette Kerry L. 
Published: May 2005

AbstractA sulfide‐resistant ctrain of Thiobacillus denitrificans, strain F, prevented the accumulation of sulfide by Desulfovibrio desulfuricans when both organisms were grown in liquid medium or in Berea sandstone cores. The wild‐type strain of T. denitrificans did not prevent the accumulation of sulfide produced by D. desulfuricans. Strain F also prevented the accumulation of sulfide by a mixed population of sulfate‐reducing bacteria enriched from an oil field brine. Fermentation balances showed that strain F stoichiometrically oxidized the sulfide produced by D. desulfuricans and the oil field brine enrichment to sulfate. These data suggest that strain F would be effective in controlling sulfide production in oil reservoirs and other environments.
Development of bioreactors for the culture of surface immobilized plant cells
Authors: Archambault J. , Volesky B. , Kurz W. G. W. 
Published: May 2005

AbstractThe scaleup of the technique of plant cell surface immobilization was performed successfully in specifically designed laboratory size bioreactors. The immobilizing matrix was formed into a vertically wound spiral providing for a high immobilizing area‐to‐volume ratio (0.8–1.2 cm−1). A modified airlift and a mechanically stirred vessel delivered a best bioreactor performance characterized by low biomass frothing and highly efficient plant cell attachment and retention (≥96%). The growth of Catharanthus roseus cells investigated in these bioreactors was found not to be mass transfer limited. It required mild mixing and aeration levels (kLa ∼ 10–15 h−1). The biomass formation pattern of surface immobilized plant cells generally exhibited a linear growth phase followed by a stationary phase characterized by the presence of residual carbohydrates in the medium, contrary to suspension cultures. This behavior was found to depend on the plant cell type and/or line cultured, as well as on the inoculum age. The space restriction and unidirectional growth of the SIPC biofilm combined with the limited availability of essential intracellular nutrients rapidly accumulated from the medium by the stationary phase inoculated plant cells all likely contributed to the culture behavior.
Simple constrained‐optimization view of acetate overflow in E. coli
Authors: Majewski R. A. , Domach M. M. 
Published: May 2005

AbstractThe production of acetate by aerobically growing E. coli is examined. The problem is formulated in terms of a flow network that has as its objective maximal ATP synthesis. It is found that when loads are imposed and flux constraints exist either at the level of NADH turnover rate or the activity of a key Krebs cycle enzyme, switching to acetate overflow is predicted. Moreover, the result found for the latter constraint can be shown to be formally equivalent to a correlation experimentally determined for the specific rate of acetate production by E. coli K‐12.
On performing experimental studies on transient states of continuous‐flow methanogenic reactors
Authors: DeLorme Allan J. , Kapuscinski Richard B. 
Published: May 2005

AbstractOne approach to exploring the behavior of microbial cultures during transient conditions of unbalanced growth is to experimentally observe continuous‐flow biological reactors which have been subjected to perturbations in the influent flowrate and/or concentration of growth‐limiting substrate. Proper interpretation of such experiments requires that appropriate account be taken of reaction stoichiometry, the distribution and abundance of microbial populations within the reactor, and the nonideality of mixing and flow distribution in the reactor. These aspects of proper experimental design are particularly critical when the system of interest involves methanogenic consortia and is not a completely‐mixed, suspended‐growth reactor.
Production of emulsan in a fermentation process using soybean oil (SBO) in a carbon–nitrogen coordinated feed
Authors: Shabtai Yossef , Wang Daniel I. C. 
Published: May 2005

AbstractA fermentation process for the microbial production of an amphipatic lipopolysaccharide, emulsan, has been established using a triglyceride carbon source in a coordinated carbon–nitrogen feed strategy. The polysaccharide was produced by the Acinetobacter strain at a productivity of about 0.5 g emulsan/L h while utilizing only the fatty acids (FA) portion of the triglycerides or free fatty acids that were fed into the medium.A useful correlation between the utilization of the fatty acids and the consumption of the nitrogen was found and employed for the practical feed strategy using an appropriate CN ratio (7.7 g C/g N) of the soybeanoil (SBO) (carbon source) to the ammonium hydroxide base (nitrogen source). Either the pH control or the supervising computer system could accomplish the adequate balanced feed in to the fermentor. Lipolysis slowdown was overcome by switching from a triglyceride carbon source to a free fatty acids one. A yield of about 0.2 g emulsan/g fatty acids was obtained and a final concentration of over 20 g/L was reached. The polymeric product was found to be partially associated with the cell‐oil complexes in the fermentation broth unless the oily carbon source was efficiently exhausted. A fedbatch fermentation that employed a shift of the carbon source feed from triglycerides to free fatty acids appeared to be an appropriate and feasible way of producing the polymer.
Heat transfer simulation in solid substrate fermentation
Authors: Saucedo‐Castañeda G. , Gutiérrez‐Rojas M. , Bacquet G. , Raimbault M. , Viniegra‐González G. 
Published: May 2005

AbstractA mathematical model was developed and tested to simulate the generation and transfer of heat in solid substrate fermentation (SSF). The experimental studies were realized in a 1‐L static bioreactor packed with cassava wet meal and inoculated with Aspergillus niger. A simplified pseudohomogeneous monodimensional dynamic model was used for the energy balance. Kinetic equations taking into account biomass formation (logistic), sugar consumption (with maintenance), and carbon dioxide formation were used. Model verification was achieved by comparison of calculated and experimental temperatures. Heat transfer was evaluated by the estimation of Biot and Peclet heat dimensionless numbers 5–10 and 2550–2750, respectively. It was shown that conduction through the fermentation fixed bed was the main heat transfer resistance. This model intends to reach a better understanding of transport phenomena in SSF, a fact which could be used to evaluate various alternatives for temperature control of SSF, i.e., changing air flow rates and increasing water content. Dimensionless numbers could be used as scale‐up criteria of large fermentors, since in those ratios are described the operating conditions, geometry, and size of the bioreactor. It could lead to improved solid reactor systems. The model can be used as a basis for automatic control of SSF for the production of valuable metabolites in static fermentors.
A mathematical model for the growth of mycelial fungi in submerged culture
Authors: Aynsley M. , Ward A. C. , Wright A. R. 
Published: May 2005

AbstractA new kinetic model is developed which provides a simple quantitative description of the growth of mycelial organisms. The main concept of this model is that the fungal hypha can be regarded as a form of self‐extending tubular reactor. Nutrients are absorbed along the length of the “reactor,” converted into cell envelope precursors and transported forward to the growth tip where they become consumed in the process of extension; Michaelis–Menten kinetics are assumed to operate at this point. The model is capable of predicting changes in the rates of hyphal extension, branching, and fragmentation during mycelial growth in submerged culture and consequently variations in the hyphal growth unit. Simulation studies using the model are presented and the results are evaluated with reference to data from an industrial‐type fed‐batch penicillin fermentation.