bluuebunny/crossref_metadata_2025_split huggingface dataset:
A thermodynamically based correlation for maintenance gibbs energy requirements in aerobic and anaerobic chemotrophic growth
Authors: Tijhuis L. , Van Loosdrecht M. C. M. , Heijnen J. J. 
Published: December 2004

AbstractA thermodynamic framework has been provided for the description of maintenance requirements of microorganisms. The central parameter is the biomass specific Gibbs energy consumption for maintenance, mE (kJ/C‐mol biomass · h). A large set of data has been used including (i) a large range of different organisms (bacteria, yeasts, plant cells), (ii) mixed cultures, (iii) heterotrophic and autotrophic growth, (iv) growth under aerobic and anaerobic conditions, and (v) a large temperature range (5–75°C). It appears that only the temperature has a major influence, with an energy of activation of 69 kJ/mol. Different electron donors or electron acceptors only show a very minor influence on mE. On the basis of the data set, temperature correlations of mE have been derived for aerobic and anaerobic growth. The generalized concept for maintenance Gibbs energy is used to establish a correlation which allows the estimation of the biomass yield on electron donor as a function of C‐source, electron donor, electron acceptor, N source, growth rate, and temperature. The advantage of using the mE parameter over other maintenance‐related parameters (like μe, mO2, mD, γDmD) is discussed. © 1993 John Wiley & Sons, Inc.
On‐line monitoring of cell concentration of Perilla frutescens in a bioreactor
Authors: Zhong Jian‐Jiang , Fujiyama Kazuhito , Seki Tatsuji , Yoshida Toshiomi 
Published: December 2004

AbstractThis article demonstrates the successful in situ real‐time monitoring of the cell concentration of Perilla frutescens in a bioreactor by using a laser turbidimeter. It was found that turbidity measurements at 780 nm with the laser sensor were hardly affected by the red color of the anthocyanin produced by P. frutescens cells, nor by the aeration rate or agitation speed within the ranges investigated. There was an excellent linear relationship, with a correlation coefficient (r2) higher than 0.99, between the sensor's response and the cell concentration. The whole growth stage of the cells, i.e., lag, logarithmic, and stationary phases, in bioreactor cultivations, could be satisfactorily estimated on‐line by means of the in situ turbidimeter. However, during the declining phase of the cells, an apparent deviation was observed between the on‐line estimations and off‐line measurements of cell concentrations by dry cell weight, while the wet cell weight could be estimated by the same turbidimeter system. We found that this deviation was caused by a decrease in the cell density due to an increase of the individual cell volume and a decrease of the cell dry weight during the declining phase. © 1993 John Wiley & Sons, Inc.
Use of a simple mathematical model to predict the behavior of Escherichia coli overproducing β‐lactamase within continuous single‐ and two‐stage reactor systems
Authors: Togna A. Paul , Fu Jeffrey , Shuler Michael L. 
Published: December 2004

AbstractA simple mathematical model is developed to help explain the complex population dynamics of an Escherichia coli host–plasmid expression/excretion system for β‐lactamase within single‐ and two‐stage reactors. The model successfully integrates the individual regulatory (tac promoter induction), genetic (runaway plasmid replication), and population dynamics (culture instability) aspects of the system. The model predicts, and experiment confirms, that high‐level β‐lactamase production and excretion cannot be easily maintained in single‐stage reactors using the current plasmid construction. Stable target protein production and excretion is mathematically predicted, and experimentally confirmed, within two‐stage reactors. The model is used to provide insight into engineering a more stable host–vector expression/excretion system for use in single‐stage reactors. © 1993 John Wiley & Sons, Inc.
Optimization of hepatocyte attachment to microcarriers: Importance of oxygen
Authors: Foy Brent D. , Lee Jaegwan , Morgan Jeff , Toner Mehmet , Tompkins Ronald G. , Yarmush Martin L. 
Published: December 2004

AbstractMany potential applications of primary hepatocytes cultured on microcarriers, such as an artificial liver or hepatocyte transplantation, would benefit from having a large number of hepatocytes attached to each microcarrier. In addition, the supply of primary hepatocytes is usually limited, so the efficient utilization of hepatocytes during attachment to microcarriers is necessary. Several physical parameters involved in the attachment process have been investigated, and the number of cells attached per microcarrier and the fraction of hepatocytes which attach have been quantitatively monitored. Variation of the partial pressure of gas phase oxygen in the incubation flask produced significant effects on the attachment of hepatocytes to microcarriers, with higher partial pressures of oxygen found to be necessary for attachment. In addition, variation of fluid depth and cell number, both of which influence the partial pressure of oxygen at the cell surface, affected hepatocyte attachment. The partial pressure of oxygen at the cell surface as a function of the physical parameters was analyzed using a simple one‐dimensional theoretical model. Variations in the cell‐to‐microcarrier ratio used for incubation indicate that a compromise must be made in terms of maximizing the number of cells per microcarrier and the fraction of total hepatocytes which attach. The maximum number of hepatocytes per microcarrier obtained in this work was approximately 100. The best attachment fraction, defined as the ratio of the number of hepatocytes attached to the total number added to the incubation, was approximately 90%. © 1993 John Wiley & Sons, Inc.
Enantioselective synthesis of ibuprofen esters in AOT/isooctane microemulsions by Candida cylindracea lipase
Authors: Hedström Gun , Backlund Maria , Slotte J. Peter 
Published: December 2004

AbstractThe enantioselective esterification of racemic ibuprofen, catalyzed by a Candida cylindracea lipase, was studied in a water‐in‐oil microemulsion (AOT/isooctane). By using n‐propanol as the alcohol, an optimal W0 ([H2O]/[AOT] ratio) of 12 was found for the synthesis of n‐propyl‐ibuprofenate at room temperature. The lipase showed high preference for the S(+)‐enantiomer of ibuprofen, which was esterified to the corresponding S(+)‐ibuprofen ester. The R(−)‐ibuprofen remained unesterified in the microemulsion. The calculated enantioselectivity value (E) for S‐ibuprofen ester was greater than 150 (conversion 0.32). The enzyme activities of n‐alcohols with different chain lengths (3–12) were compared, and it appeared that short‐ (propanol and butanol) and long‐chained (decanol and dodecanol) alcohols were better substrates than the intermediate ones (pentanol, hexanol, and octanol). However, unlike secondary and tertiary alcohols, all of the tested primary alcohols were substrates for the lipase. The reversible reaction (i.e., the hydrolysis of racemic ibuprofen ester in the microemulsion) was also carried out enantioselectively by the enzyme. Only the S form of the ester was hydrolyzed to the corresponding S‐ibuprofen. The reaction yield was, however, only about 4% after 10 days of reaction. The corresponding yield for the esterification of ibuprofen was about 35% (10 days). The high enantioselectivity displayed by the lipase in the microemulsion system was seen neither in a similar esterification reaction in a pure organic solvent system (isooctane) nor in the hydrolysis reaction in an aqueous system (buffer). The E value for S‐ibuprofen ester in the isooctane system was 3.0 (conversion 0.41), and only 1.3 for S‐ibuprofen in the hydrolysis reaction (conversion 0.32). The differences in enantioselectivity for the lipase in various systems are likely due to interfacial phenomena. In the microemulsion system, the water in which the enzyme is dissolved is separated from the solvent by a layer of surfactant molecules, thus creating an interface with a relatively large area. Such interfaces are not present in the pure organic solvent systems (no surfactant) nor in aqueous systems. © 1993 John Wiley & Sons, Inc.
Prevascularization of porous biodegradable polymers
Authors: Mikos Antonios G. , Sarakinos Georgios , Lyman Michelle D. , Ingber Donald E. , Vacanti Joseph P. , Langer Robert 
Published: December 2004

AbstractHighly porous biocompatible and biodegradable polymers in the form of cylindrical disks of 13.5 mm diameter were implanted in the mesentery of male syngeneic Fischer rats for a period of 35 days to study the dynamics of tissue ingrowth and the extent of tissue vascularity, and to explore their potential use as substrates for cell transplantation. The advancing fibrovascular tissue was characterized from histological sections of harvested devices by image analysis techniques. The rate of tissue ingrowth increased as the porosity and/or the pore size of the implanted devices increased. The time required for the tissue to fill the device depended on the polymer crystallinity and was smaller for amorphous polymers. The vascularity of the advancing tissue was consistent with time and independent of the biomaterial composition and morphology. Poly(L‐lactic acid) (PLLA) devices of 5 mm thickness, 24.5% crystallinity, 83% porosity, and 166 μm median pore diameter were filled by tissue after 25 days. However, the void volume of prevascularized devices (4%) was minimal and not practical for cell transplantation. In contrast, for amporphous PLLA devices of the same dimensions, and the similar porosity of 87% and median pore diameter of 179 μm, the tissue did not fill completely prevascularized devices, and an appreciable percentage (21%) of device volume was still available for cell engraftment after 25 days of implantation. These studies demonstrate the feasibility of creating vascularized templates of amorphous biodegradable polymers for the transplantation of isolated or encapsulated cell populations to regenerate metabolic organs and tissues. © 1993 John Wiley & Sons, Inc.
Removal of lead from aqueous solutions by Penicillium biomass
Authors: Niu Hui , Xu Xue Shu , Wang Jian Hua , Volesky B. 
Published: December 2004

AbstractThe removal of lead ions from aqueous solutions by adsorption on nonliving Penicillium chrysogenum biomass was studied. Biosorption of the Pb+2 ion was strongly affected by pH. Within a pH range of 4 to 5, the saturated sorption uptake of Pb+2 was 116 mg/g dry biomass, higher than that of activated charcoal and some other microorganisms. At pH 4.5, P. chrysogenum biomass exhibited selectivity for Pb+2 over other metal ions such as Cd+2, Cu+2, Zn+2, and As+3 Sorption preference for metals decreased in the following order: Pb > Cd > Cu > Zn > As. The sorption uptake of Pb+2 remained unchanged in the presence of Cu+2 and As+3, it decreased in the presence of Zn+2, and increased in the presence of Cd+2. © 1993 John Wiley & Sons, Inc.
Self‐cycling fermentation in a stirred tank reactor
Authors: van Walsum G. Peter , Cooper David G. 
Published: December 2004

AbstractSelf‐cycling fermentations (SCFs) were conducted in a stirred tank apparatus using Bacillus subtilis and Acinetobacter calcoaceticus. The systems were very stable and the experiments lasted through many cycles. The variation of parameters such as biomass and doubling time from cycle to cycle was small. The stirred tank reactor (STR) allowed a much better control of the working volume in the fermentor from cycle to cycle, compared to the cyclone column, and it was not necessary to make periodic corrections.The production of surfactin from B. subtilis was achieved without extending the cycle time. The harvested broth at the end of each cycle was allowed to remain in a secondary vessel, at ambient temperature, before being collected. It is exhaustion of the limiting nutrient which causes an increase in dissolved oxygen (DO). At this point, the computer, which constantly monitors the DO, triggered the harvesting sequence to end the cycle. Thus, the mature culture in the secondary vessel experienced appropriate conditions for the production of the secondary metabolite. Meanwhile, the next batch of cells was being grown in the primary reactor.The response of a gas analyzer on the effluent paralleled that of the DO measurements in the fermentor. These data for oxygen and carbon dioxide exhibited less noise than the DO readings. Either would be a more reliable parameter for feedback control of the SCF because the problem of fouling of the DO probe after extended runs of many cycles would be eliminated. © 1993 John Wiley & Sons, Inc.
Real‐Time compensation of the inner filter effect in high‐density bioluminescent cultures
Authors: Konstantinov Konstantin B. , Dhurjati Prasad , Van Dyk Tina , Majarian William , Larossa Robert 
Published: December 2004

AbstractBioluminescence has recently become a popular research tool in several fields, including medicine, pharmacology, biochemistry, bioprocessing, and environmental engineering. Beginning with purely qualitative goals, scientists are now targeting more demanding applications where accurate, quantitative interpretation of bioluminescence is necessary. Using the recent advances in fiber‐optic technology, bioluminescence is easily monitored in vivo and in real time. However, the convenience of this measurement is often concealing an unsuspected problem: the bioluminescence signal might be corrupted by a large error caused by the extinction of light by biological cells. Since bioluminescent cultures not only emit light but also absorb and scatter it, the measured signal is related in a complex, nonlinear, and cell‐concentration‐dependent manner to the “true” bioluminescence. This light extinction effect, known as the “inner filter effect,” is significant in high‐density cultures. Adequate interpretation of the bioluminescence signal can be difficult without its correction. Here, we propose a real‐time algorithm for elimination of the inner filter effect in a bioreactor. The algorithm yields the bioluminescence which would be measured if the glowing culture was completely transparent. This technique has been successfully applied to batch and continuous cultivation of recombinant bioluminescent Escherichia coli. © 1993 John Wiley & Sons, Inc.
Use of ATP to characterize biomass viability in freely suspended and immobilized cell bioreactors
Authors: Gikas P. , Livingston A. G. 
Published: December 2004

AbstractThis work describes investigations into the viability of cells growing on 3,4‐dichloroaniline (34DCA). Two bioreactors are employed for microbial growth, a continuous stirred tank (CST) bioreactor with a 2‐L working volume, and a three‐phase air lift (TPAL) bioreactor with a 3‐L working volume. Experiments have been performed at several dilution rates between 0.027 and 0.115 h−1 in the CST bioreactor and between 0.111 and 0.500 h−1 in the TPAL bioreactor. The specific ATP concentration was calculated at each dilution rate in the suspended biomass in both bioreactors as well as in the immobilized biomass in the TPAL bioreactor. The ATP was extracted from the cells using boiling tris‐EDTA buffer (pH 7.75), and the quantity determined using a firefly (bioluminescence) technique. The cultures were inspected under an electron microscope to monitor compositional changes. Results from the CST bioreactor showed that the biomass‐specific ATP concentration increases from 0.44 to 1.86 mg ATP g−1 dry weight (dw) as dilution rate increases from 0.027 to 0.115 h−1. At this upper dilution rate the cells were washed out. The specific ATP concentration reached a limiting average value of 1.73 mg ATP g−1 dw, which is assumed to be the quantity of ATP in 100% viable biomass. In the TPAL bioreactor, the ATP level increased with dilution rate in both the immobilized and suspended biomass. The specific ATP concentration in the immobilized biomass increased from approximately 0.051 mg ATP g−1 dw at dilution rates between 0.111 and 0.200 h−1 to approximately 0.119 mg ATP g−1 dw at dilution rates between 0.300 and 0.500 h−1. This indicates that the immobilized biomass contained a viable cell fraction of around 5%. Based on these results, kinetic data for freely suspended cells should not be applied to the modeling of immobilized cell systems on the assumption that immobilized biomass is 100% viable. © 1993 John Wiley & Sons, Inc.
Differences in response of Zymomonas mobilis and Saccharomyces cerevisiae to change in extracellular ethanol concentration
Authors: Hobley T. J. , Pamment N. B. 
Published: December 2004

AbstractIn high cell density batch fermentations, Zymomonas mobilis produced 91 g L−1 ethanol in 90 min but culture viability fell significantly. Similar viability losses in rapid fermentations by yeast have recently been shown to be attributable in part to the high rate of change of the extracellular ethanol concentration. However, in simulated rapid fermentations in which ethanol was pumped continuously to low cell density Z. mobilis suspensions, increases in the rate of change of ethanol concentration in the range 21–83 g L−1 h−1 did not lead to accelerated viability losses. The lag phase of Zymomonas cultures exposed to a 30‐g L−1 step change in ethanol concentration was much shorter than that of Saccharomyces cerevisiae, providing evidence that the comparative insensitivity of Zymomonas to high rates of change of ethanol concentration is due to its ability to adapt to changes in ethanol concentration more rapidly than yeast. © 1994 John Wiley & Sons, Inc.
Diffusivity of Cu2+ in calcium alginate gel beads
Authors: Jang Larry K. 
Published: December 2004

AbstractThe diffusivity of Cu2+ in calcium alginate beads calculated by the shrinking core model (SCM) was reevaluated in this work. The results obtained in this work were significantly different than those by the original authors. There were excellent agreements between the results obtained by the SCM in this work and those by the more rigorous linear absorption model (LAM) by the original authors. © 1994 John Wiley & Sons, Inc.
Immobilization of a proteinase from the extremely thermophilic organism Thermus Rt41A
Authors: Wilson S.‐A. , Peek K. , Daniel R. M. 
Published: December 2004

AbstractAn extracellular proteinase from Thermus strain Rt41A was immobilized to controlled pore glass (CPG) beads. The properties of the free and CPG‐immobilized enzymes were compared using both a large (azocasein) and a small (peptidase) substrate. The specific activity of the immobilized proteinase was 5284 azoU/mg with azocasein and 144 sucU/mg for SucAAPFpNA. The percentage recovery of enzyme activity was unaffected by pore size when it was immobilized at a fixed level of activity/g of beads, whereas it increased with increasing pore size when added at a fixed level/m2 of support. Saturation of the CPG beads was observed at 540 azoU/m2 of 105‐nm beads. Lower levels (50 azoU/m2 of 50‐nm beads) were used in characterization experiments. The pH optimum of the immobilized Rt41A proteinase was 8.0 for azocasein and 9.5 for SucAAPFpNA, compared with the free proteinase which was 10.5 for both substrates. The immobilized enzyme retained 65% of its maximum activity against azocasein at pH 12, whereas the free proteinase retained less than 10% under the same conditions. Stability at 80°C increased on immobilization at all pH values between 5 and 11, the greatest increase in half‐life being approximately 12‐fold at pH 7.0. Temperature–activity profiles for both the free and immobilized enzymes were similar for both substrates. The stability of the immobilized proteinase, however, was higher than that of the free enzyme in the absence and presence of CaCl2. Overall, the results show that low levels of calcium (10 μM) protect against thermal denaturation, but that high calcium or immobilization are required to protect against autolysis. © 1994 John Wiley & Sons, Inc.
Two‐Step biocatalytic conversion of an ester to an aldehyde in reverse micelles
Authors: Yang Fangxiao , Russell Alan J. 
Published: December 2004

AbstractLipases from Candida cyclindracea (L‐1754) and wheat germ (L‐3001) have been used to hydrolyze esters to their corresponding alcohols and acids in reverse micelles. Alcohol dehydrogenase from baker's yeast (YADH) was subsequently used to reduce the alcohol products to aldehydes. Cofactor recycling in the redox reaction was achieved using a sacrificial cosubstrate, as described previously. Four surfactants (sodium dioctylsulfosuccinate, Nonidet P‐40 with Triton X‐35, polyoxyethylene, 10‐cetyl‐ether, polyoxyethylene sorbitan trioleate) were employed to determine the effect of amphiphile on ester hydrolysis and redox reaction rates separately. The effect of type of organic solvent, W0 [(water]/[surfactant)], and substrate concentration on separte enzyme activity were also investigated. A brief investigation of a single phase, two‐step reaction catalyzed by the combination of lipase and YADH in reverse micelles is also reported. The activities of the enzymes are significantly different when used together instead of independently. © 1994 John Wiley & Sons, Inc.
Separation of penicillin G from phenylacetic acid in a supported liquid membrane system
Authors: Lee Chan‐Jen , Yeh Huey‐Jiuan , Yang Wu‐Yung , Kan Chin‐Rang 
Published: December 2004

AbstractThe separation of penicillin G (Pen G) from phenylacetic acid (PAA) by use of a supported liquid membrane (SLM) system with Amberlite LA‐2 dissolved in 1‐decanol, supported on a microporous polypropylene membrane, was studied. The results show that the individual permeability of each component in mixture was lower than that in a single compartment system and, it suggests a strong transport competition between Pen G and PAA. The SLM system in this study proved to be a promising process for the selective separation of Pen G from PAA. The maximum separation factor was found to be 1.8 under a liquid membrane resistance controlled mechanism. © 1994 John Wiley & Sons, Inc.
Purification of a recombinant protein produced in a baculovirus expression system by immobilized metal affinity chromatography
Authors: Wang Min‐Ying , Bentley William E. , Vakharia Vikram 
Published: December 2004

AbstractOver the past 10 years, the baculovirus–insect cell system has become a powerful and versatile tool for the expression of a variety of heterologous proteins. In order to simplify separation of a cloned protein from the baculovirus–insect expression system, we have cloned a gene encoding for the protein of interest, a structural protein (VP2) of a strain (E/DEL) of infectious bursal disease virus (IBDV), with a metal ion binding site (His)5 at its C‐terminus. This chimeric protein (VP2H) has been expressed and one‐step affinity purified with immobilized metal ions (Ni+2). With antigen capture–enzyme‐linked immunosorbent assay (AC‐ELISA), we determined that the conformation of this chimeric protein was no different from the recombinant wild‐type VP2 protein. However, the two proteins (VP2 and VP2H) can be distinguished and resolved by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and detected immunologically following Western blotting. © 1994 John Wiley & Sons, Inc.