bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass transfer effects in solvent‐free fat interesterification reactions: Influences on catalyst design
Authors: Ison A. P. , Macrae A. R. , Smith C. G. , Bosley J. 
Published: December 2004

AbstractThe use of solvent‐free systems in the oil and fats industry is commonplace. Initial studies on interesterification were carried out in solvent systems because the lipase was immobilized solely by adsorption onto particles of diatomaceous earth. In this study, the mass transfer characteristics associated with the continuous interesterification of olive oil in a solvent‐free system have been examined, for lipase immobilized on the three ion‐exchange materials: Duolite ES562, Duolite ES568, and Spheroil DEA. The process of immobilization is influenced by the internal structure of the material and this in turn influences the interesterification activity of the catalyst. Individually prepared catalysts for the three support materials have shown that external mass transfer limitations are unlikely even at low flowrates.In the case of Spherosil DEA, with a mean pore diameter of 1480 Å, the wide pores would be expected to reduce internal mass transfer limitations; however, it is more likely that the reduction in activity with increased catalyst loading is due to the lipase molecules being immobilized in a tightly packed monolayer. In such a situation, some active sites of the lipase molecules would become inaccessible to substrate molecules leading to an observed reduction in activity. For Duolite ES568, the observed results are very similar to those seen for Spherosil DEA, however, the pore structure of this support material indicate that some internal mass transfer limitations may also be occurring. Yet the contribution of the individual effects cannot be determined. The results observed for the support Duolite ES562 are different than those observed for the other materials and reflect the heterogeneity of Duolite ES562. The large proportion of narrow pores in the support mean that, for the catalysts examined, immobilization is most likely to have occurred in the external pores of the particles, and as such no internal mass transfer limitation is observed.It is clear that for interesterification the material chosen for enzyme immobilization will have an important role in determining the catalyst efficiency. External mass transfer limitations are very minor and observed internal mass transfer limitations may be caused by both internal mass transfer and the manner in which the immobilization process occurs. © 1994 John Wiley & Sons, Inc.
Oxygen uptake and citric acid production by Candida lipolytica Y 1095
Authors: Rane Kishore D. , Sims Kevin A. 
Published: December 2004

AbstractThe rates of oxygen uptake and oxygen transfer during cell growth and citric acid production by Candida lipolytica Y 1095 were determined. The maximum cell growth rate, 1.43 g cell/L · h, and volumetric oxygen uptake rate, 343 mg O2/L · h, occurred approximately 21 to 22 h after inoculation. At the time of maximum oxygen uptake, the biomass concentration was 1.3% w/v and the specific oxygen uptake rate was slightly greater than 26 mg O2/g cell · h. The specific oxygen uptake rate decreased to approximately 3 mg O2/g cell · h by the end of the growth phase.During citric acid production, as the concentration of dissolved oxygen was increased from 20% to 80% saturation, the specific oxygen uptake and specific citric acid productivity (mg citric acid/g cell · h) increased by 160% and 71%, respectively, at a biomass concentration of 3% w/v. At a biomass concentration of 5% w/v, the specific oxygen uptake and specific citric acid productivity increased by 230% and 82%, respectively, over the same range of dissolved oxygen concentrations.The effect of dissolved oxygen on citric acid yields and productivities was also determined. Citric acid yields appeared to be independent of dissolved oxygen concentration during the initial production phase; however, volumetric productivity (g citric acid/L · h) increased sharply with an increase in dissolved oxygen. During the second or subsequent production phase, citric acid yields increased by approximately 50%, but productivities decreased by roughly the same percentage due to a loss of cell viability under prolonged nitrogen‐deficient conditions. © 1994 John Wiley & Sons, Inc.
Ethanol production from nonsterilized carob pod extract by free and immobilized Saccharomyces cerevisiae cells using fed‐batch culture
Authors: Roukas T. 
Published: December 2004

AbstractThe production of ethanol from carob pod extract by free and immobilized Saccharomyces cerevisiae cells in batch and fed‐batch culture was investigated. Fed‐batch culture proved to be a better fermentation system for the production of ethanol than batch culture. In fed‐batch culture, both free and immobilized S. cerevisiae cells gave the same maximum concentration (62 g/L) of final ethanol at an initial sugar concentration of 300 g/L and F = 167 mL/h. The maximum ethanol productivity (4.4 g/L h) was obtained with both free and immobilized cells at a substrate concentration of 300 g/L and F = 334 mL/h. In repeated fed‐batch culture, immobilized S. cerevisiae cells gave a higher overall ethanol concentration compared with the free cells. The immobilized S. cerevisiae cells in Ca‐alginate beads retained their ability to produce ethanol for 10 days. © 1994 John Wiley & Sons, Inc.
Selective protein transport through a thin cellulose coated porous membrane
Authors: Yang Yiting , Jacobs Harvey , Bae You Han , Kim Sung Wan 
Published: December 2004

AbstractA new composite membrane was designed and studied for permselectivity of various molecular weight proteins. The membrane is composed of a porous substrate membrane [Durapore; poly(vinylidene fluoride)] coated with a thin dense layer of regenerated cellulose. This composite membrane was fabricated by spin coating a cellulose acetate solution onto the membrane, followed by alkaline hydrolysis of the cellulose acetate coating to regenerate cellulose. The coated layer was physically characterized by scanning electron microscopy (SEM) and infrared (IR) spectroscopy. In addition, the water uptake into and permeation properties of macromolecules across the coated and uncoated membranes were studied. A typical composite membrane coating was 0.8 ± 0.2 μm thick, resulting in a molecular weight cutoff of approximately 40,000 daltons. This composite membrane also demonstrated negligible diffusional lag time for permeants, due to the diffusional barrier. © 1994 John Wiley & Sons, Inc.
Biosensor for continuos glucose monitoring
Authors: Atanasov Plamen , Wilkins Ebtisam 
Published: December 2004

AbstractA potentially implantable glucose biosensor for continuous monitoring of glucose levels in diabetic patients has been developed. The glucose biosensor is based on an amperometric oxygen electrode and glucose oxidase immobilized on carbon powder held in a form of a liquid suspension. The enzyme material can be replaced (the sensor recharged) without sensor disassembly. Recharging of the biosensor is achieved by injecting fresh immobilized enzyme into the sensor using a septum. Diffusion membranes made of silastic latex‐rubber coatings over a microporous polycarbonate membrane are used. Calibration curves of the amperometric signal show linearity over a wide range of glucose concentrations—up to 500 mg/dL (28 mM), covering hypoglycemic, normoglycemic, and hyperglycemic conditions. Preliminary in vitro studies of the biosensor show stable performance during several recharge cycles (of 14 days each) over a period of 4 months. © 1994 John Wiley & Sons, Inc.
Modeling hexavalent chromium reduction in Escherichia coli 33456
Authors: Shen Hai , Wang Yi‐Tin 
Published: December 2004

AbstractA model based on te analysis of the mechanism of enzymatic reactions was developed to characterize the rate and extent of microbial reduction of hexavalent chromium in Escherichia coli 33456. A finite reduction capacity (Rc) was proposed and incorporated into the enzymatic model to regulate the toxicity effect on cells due to the oxidizing power of Cr(VI). The parameter values were determined by nonlinear least‐square analysis using experimental data of anaerobic cultures. The obtained parameters were then used to predict Cr(VI) reduction in aerobic cultures along with a modification term of uncompetitive inhibition from molecular oxygen. The applicability of the developed model was demonstrated through excellent prediction of the results of batch studies conducted over range of initial Cr(VI) concentrations, initial cell densities, and DO levels. A sensitivity analysis revealed that the parameters obtained using the experimental data were unique, and neither change in Kc, the half‐velocity constant, at high initial Cr(VI) concentrations nor change in Rc, the reduction capacity, at low initial Cr(VI) concentrations was sensitive to model prediction. © 1994 John Wiley & Sons, Inc.
Optimization of an industrial microalgae fermentation
Authors: Hilaly A. K. , Karim M. N. , Guyre D. 
Published: December 2004

AbstractOptimization of cellular productivity of an industrial microalgae fermentation was investigated. The fermentation was carried out at Coors Biotech Products Company, Fort Collins, Colorado. A mathematical model was developed based on the data collected from pilot plant test runs at different operating conditions. Pontryagin's maximum principle was used for determining the optimal feed policy. A feedback control algorithm was also studied for maximizing the cellular productivity. During continuous operation, the optimum dilution rate was determined by an adaptive optimization scheme based on the steepest descent technique and a recursive least squares estimation of model parameters. A direct search algorithm was also applied to determine the optimum feed rate. Comparison of the theoretical results of the different optimization schemes revealed that the direct search algorithm was preferable because of its simplicity. The experimental results of real time application of the feedback algorithm agreed fairly well with those of the theoretical analyses. © 1994 John Wiley & Sons, Inc.
Inactivation of enzymes by organic solvents: New technique with well‐defined interfacial area
Authors: Ghatorae Amreek S. , Bell George , Halling Peter J. 
Published: December 2004

AbstractA liquid‐liquid bubble column apparatus allows exposure of enzyme solutions to water‐immiscible organic solvents with a known total interfacial area and welldefined time scales and flow. It allows clear distinction of the different classes of inactivation mechanism. With urease as a model enzyme, octan‐2‐one and butylbenzene act only through the effects of solvent molecules dissolved in the aqueous phase, giving first‐order inactivation at 0.34 and 0.21 h−1, respectively. Hexane and tridecane act only through exposure to the interface. The amount of urease inactivated is proportional to the total area of interface exposed, rather than to elapsed time, and may be characterized by a rate of about 0.5 μkat m−2. This is consistent with the formation and (partial) inactivation of a complete adsorbed monolayer of protein. With butan‐1‐ol, both mechanisms contribute significantly to the observed inactivation. The presence of O2 increases the rate of interfacial inactivation, but not that by dissolved solvent. © 1994 John Wiley & Sons, Inc.
Electrochemical disinfection of bacteria in drinking water using activated carbon fibers
Authors: Matsunaga Tadashi , Nakasono Satoshi , Kitajima Yoji , Horiguchi Kazuo 
Published: December 2004

AbstractA novel electrochemical reactor employing activated carbon fiber (ACF) electrodes was constructed for disinfecting bacteria in drinking water. Escherichia coli adsorbed preferentially onto ACF rather than to carbon‐cloth or granular‐activated carbon. E. coli cells, which adsorbed onto the ACF, were killed electrochemically when a potential of 0.8 V vs. a saturated calomel electrode (SCE) was applied. Drinking water was passed through the reactor in stop‐flow mode: 2mL/min for 12 h, o L/min for 24 h, and 1 mL/min for 6 h. At an applied potential of 0.8 V vs, SCE, viable cell concentration reamined below 30 cells/mL. In the absence of an applied potential, bacteria grew to a maximum concentration of 9.5 × 103 cells/mL. After continuous operation at 0.8 V vs. SCE, cells adsorbed onto the ACF could not be observed by scanning electron microscopy. In addition, chlorine in drinking water was completely removed by the reactor. Therefore, clean and efficient inactivation of bacteria in drinking water was successfully performed. © 1994 John Wiley & Sons, Inc.
Monitoring recombinant inclusion body recovery in an industrial disc stack centrifuge
Authors: Jin K. , Thomas O. R. T. , Dunnill P. 
Published: December 2004

AbstractA simple and rapid spectrophotometric method for measuring recombinant inclusion body concentrations in the presence of Escherichia coli cell debris has been applied to monitoring the performance of an industrial disc stack centrifuge. Turbidimetric measurements were made at two wavelengths, i.e., 600 nm and 420 nm, and the ratios of OD600nm/OD420nm related to the particle composition in suspension. The principle behind the technique is that inclusion body particles scatter light at 600 nm more effectively than do smaller cell debris particles when compared with the degree of light scatter at 420 nm. This technique may have broad potential application in developing an automatic monitoring and control system for industrial‐scale inclusion body recovery. © 1994 John Wiley & Sons, Inc.
Biological destruction of CCl4: I. Experimental design and data
Authors: Petersen James N. , Skeen Rodney S. , Amos Kristine M. , Hooker B. S. 
Published: December 2004

AbstractA denitrifying consortium capable of transforming carbon tetrachloride (CCl4) was cultured from aquifer sediment from the U.S. Department of Energy's Hanford Site in southeastern Washington State. To understand the kinetics of the biological destruction of CCl4 by these microbes, a set of experiments, the conditions of which were chosen according to a fractional factorial experimental design, were completed. This article reports on the experimental design along with the results for CCl4, biomass, acetate, nitrate, and nitrite concentrations. These data indicate that growth is inhibited by high nitrite concentrations, whereas CCl4 degradation is slowed by the presence of nitrate and/or nitrite. © 1994 John Wiley & Sons, Inc.
Mechanism of extraction of chymotrypsin into isooctane at very low concentrations of aerosol OT in the absence of reversed micelles
Authors: Paradkar Vikram M. , Dordick Jonathan S. 
Published: December 2004

AbstractChymotrypsin is easily extracted from an aqueous solution into isooctane containing the anionic surfactant aerosol OT (AOT). The concentration of AOT needed to efficiently extract 0.5 mg/mL CMT is as low as 1 mM and as low as 0.2 mM AOT was sufficient to extract the protein into isooctane. The extraction process was unaffected by 10% (v/v) ethyl acetate in the isooctane phase. Moreover, spectroscopic analysis by electron paramagnetic resonance indicated that CMT did not exist inside a discreet water pool of a reversed micelle. Calculations of the number of AOT molecules associated per extracted CMT molecule indicate that only ca. 30 surfactant molecules interact with the protein, a value too low for reversed micellar incorporation of the protein in isooctane. These studies suggested that reversed micelles do not need to be involved in the actual transfer of the protein from the aqueous to the organic phase and protein solubilization in the organic phase is possible in the absence of reversed micelles. Based on these findings, a new mechanism has been proposed herein for protein extraction via the phase transfer method involving ionic surfactants. The central theme of this mechanism is the formation of an electrostatic complex between CMT and AOT at the aqueous/organic interface between AOT and CMT, thereby leading to the formation of a hydrophobic species that partitions into the organic phase. Consistent with this mechanism, the efficiency of extraction is dependent on the interfacial mass transfer, the concentrations of CMT and AOT in the aqueous and organic phases, respectively; the ionic strength of the aqueous phase; and the presence of various cosolvents. © 1994 John Wiley & Sons, Inc.
Serum‐free media for cultures of primitive and mature hematopoietic cells
Authors: Sandstrom Craig E. , Miller William M. , Papoutsakis Eleftherios T. 
Published: December 2004

AbstractThe in vitro culture of human hematopoietic cells has many research and therapeutic applications. Traditionally, human hematopoietic cultures have been conducted using serum‐containing media. The disadvantages inherent in the use of serum could be eliminated by the use of serum‐free media. In this review, we summarize and discuss the current status of serum‐free media for both mature and immature human hematopoietic cells. The mature hematopoietic cells discussed are of lymphoid (e.g., lymphokine activated killer cells and tumor infiltrating lymphocytes) and myeloid origin (e.g., monocytes/macrophages). The cultures of immature hematopoietic cells discussed are clonogenic and long‐term cultures. In addition, we briefly review the types of human hematopoietic cells, their clinical applications, and the basic strategies and components used to formulate serum‐free media, Finally, we outline future requirements and directions in the development of serum‐free media for primitive hematopoietic cells.
Development of a bilayered living skin construct for clinical applications
Authors: Wilkins Leon M. , Watson Stephen R. , Prosky Stefan J. , Meunier Susan F. , Parenteau Nancy L. 
Published: December 2004

AbstractAn in vitro construct of human skin (living skin equivalent, LSE) has been engineered using serially passaged human epidermal keratinocytes and human dermal fibroblasts with a matrix of type I collagen. Cells are obtained from neonatal foreskin. LSE is cast, cultured, and shipped in a single culture insert. The size and shape of theinsert determines thesize and shape of the LSE. The dermal matrix consists of dermal fibroblasts within a condensed collagen lattice. The overlying epidermis is developed at the air–liquid interface to generate a protective cornified layer. Serum was not necessaryfor development of the epidermis. LSE for graft (Graftskin) has handling characteristics similar to split‐thickness skin allowing it to be meshed, stapled, and sutured. LSE was cryopreserved using 65% glycerol an rapid freezing. Viability and in vivo performance on athymic mice were similar to fresh LSE. Cells derived from human eccrine gland were able to invade and form tubules rudimentary appendages may be possible.
Leuconostoc mesenteroides growth kinetics with application to bacterial profile modification
Authors: Lappan Raymond E. , Fogler H. Scott 
Published: December 2004

AbstractBacterial profile modification (BPM) is being developed as an oil recovery technique that uses bacteria to selectively plug oil depleted zones within a reservoir to divert displacing fluids (typically water) into oil‐rich zones. Leuconostoc mesenteroides, which produces dextran when supplied with sucrose, is a bacterium that is technically feasible for use in profile modification. However, the technique requires controlled bacterial growth to produce selective plugging.A kinetic model for the production of cells and polysaccharides has been developed for L. mesenteroides bacteria. This model, based on data from batch growth experiments, predicts saccharide utilization, cell generation, and dextran production. The underlying mechanism is the extracellular breakdown of sucrose into glucose and fructose and the subsequent production of polysaccharide (dextran). The monosaccharides are then available for growth. Accompanying sucrose consumption is the utilization of yeast extract. The cell requires a complex media that is provided by yeast extract as a source of vitamins and amino acids. Varying the concentration ratio of yeast extract to sucrose in the growth media provides a means of controlling the amount of polymer produced per cell. Consequently, in situ bacteria growth can be controlled by the manipulation of nutrient media composition, thereby providing the ability to create an overall strategy for the use of L. mesenteroides bacteria for profile modification.
Production of poly(3‐hydroxybutyric acid) by fed‐batch culture of Alcaligenes eutrophus with glucose concentration control
Authors: Kim Beom Soo , Lee Seung Chul , Lee Sang Yup , Chang Ho Nam , Chang Yong Keun , Woo Seong Ihl 
Published: December 2004

AbstractAlcaligenes eutrophus NCIMB 11599 was cultivated to produce poly(3‐hydroxybutyric acid) (PHB) from glucose by the automatic fed‐batch culture technique. The glucose concentration of the culture broth was controlled at 10 to 20 g/L by two methods: using exit gas data obtained from a mass spectrometer and using an on‐line glucose analyzer. The effect of ammonium limitation on PHB synthesis at different culture phases was studied. The final cell concentration, PHB concentration, and PHB productivity increased as ammonia feeding was stopped at a higher cell concentration. High concentrations of PHB (121 g/L) and total cells (164 g/L) were obtained in 50 h when ammonia feeding was stopped at the cell concentration of 70 g/L. The maximum PHB content reached 76% of dry cell weight and the productivity was 2.42 g/L h with the yield of 0.3 g PHB/g glucose.
Protease‐catalyzed synthesis of oligopeptides in heterogenous substrate mixtures
Authors: López‐Fandiño Rosina , Gill Iqbal , Vulfson Evgeny N. 
Published: December 2004

AbstractA systematic study of enzymatic peptide synthesis in heterogeneous substrate mixtures was carried out, with the aim of establishing the preparative scope of this methodology. Semiliquid eutectics were obtained with various combinations of neutral, acidic, and basic amino acid derivatives, in the presence or absence of adjuvants. A range of serine cysteine, and metalloproteases readily catalyzed the formation of the required dipeptides under these conditions. The synthetic usefulness of the approach was demonstrated by the sequential and convergent synthesis of derivatives of a number of bioactive di‐, tri‐, and pentapeptides, including aspartame, sweet lysine peptide, kyotorphin amide, ACE‐inhibiting and ‐immunoactive tripeptides, and Leu‐enkephalin amide, with overallyields of 21% to 84% and productivities of 0.13 to 0.75 g/g being obtained. © 1994 John Wiley & Sons, Inc.
Synthesis of AcPheLeuNH2 by α‐chymotrypsin in TTAB reversed micelles: Application of response surface methodology to the optimization of the system
Authors: Serralheiro M. L. M. , Cabral J. M. S. 
Published: December 2004

AbstractThe influence of the long chain alcohols, hexanol, octanol, and decanol, as cosurfactants of the reverse micellar system of tetradecyltrimethylammonium bromide on the α‐chymotrypsin‐mediated AcPheLeuNH2 synthesis was studied. The effect of temperature, buffer molarity, pH, and substrate concentration was also evaluated. The enzyme was chemically modified and the effect of this modification upon the enzyme activity was also analyzed. Octanol allowed a higher activity for both enzyme forms. The peptide synthesis/substrate hydrolysis ratio is independent of the long chain alcohol used. The chemical modification decreases the α‐chymotrypsin activity under the system conditions studied, but increases the initial velocity of peptide synthesis relative to the ester substrate hydrolysis. The response surface methodology was applied to optimize the dipeptide synthesis in the system containing octanol as cosurfactant. © 1994 John Wiley & Sons, Inc.