摘要:

AbstractSeptic shock syndrome is a potentially fatal medical condition that is associated with elevated blood levels of low molecular weight proteins known as cytokines. Adsorption was investigated as a potential method for removing cytokines from blood. Saline with 50 mg/mL human serum albumin (HAS) spiked with pathological concentrations (ng‐pg/mL) of radiolabeled cytokine was used to study cytokine adsorption. Adsorption isotherms were linear in the pathological concentration range, with adsorption constants ranging from 33.0 mL/g to 173 mL/g for tumor necrosis factor (TNF‐α), interleukin‐8 (IL‐8),interleukin‐6 (IL‐6), and C3a. Adsorption constants were also determined for interleukin‐1α (IL‐1α), IL‐1β, and interferon‐γ (IFN‐γ). The adsorption of cytokines by several different silica adsorbents was investigated. Increased concentrations of NaCl reduced cytokine adsorption, but did not completely eliminate adsorption even at high concentrations, suggesting that adsorption wads not entirely electrostatic in nature. Possible mechanisms of cytokine adsorption are discussed. Data for batch adsorption for TNF‐α was used to estimate the minimum amount of silica required to treat septic shock. It was concluded that a silica adsorbent has a sufficiently high capacity to be used for hemoperfusion. Adsorption of myoglobin and cytochromecwas also investigated as possible marker proteins for future dynamic adsorption studies in hemoperfusion device

ISSN:0006-3592    

DOI:10.1002/bit.260440902

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe interaction of dilute mixtures of proteins and ABC triblock methacrylic polyampholytes at different values of pH was investigated turbidimetrically. The onset of interaction was manifested by large changes in turbidity at certain critical pHs which lie close to the isoelectric points of the two interacting components. Protein precipitation yields in protein‐polyampholyte binary mixtures followed the corresponding turbidity profiles and varied from 10% to 90%. The synthetic polyampholytes self‐aggregate around their isoelectric point. The kinetics of precipitation of one of the same polymer with soybean trypsin inhibitor were studied, with turbidity‐based characteristic times (exponential fit) of 2–3 min. The kinetics of precipitation of the protein‐polymer mixture are slower than that of pure polymer because a small, but steady, long‐term increase in turbidity is observed in the former case. The pH‐dependence of the turbidity of binary mixtures of one protein and one synthetic polyampholyte, as well as a tertiary mixture of two proteins and one polyampholyte, were measured 30 min after the pH adjustment. The observations in these experiments along with the measured protein precipitation yields in the binary mixtures and the polyampholyte self‐aggregation can be used for polymer removal and recycling. The latter constitutes a significant advantage over the use of homopolyelectrolytes which cannot easily be recycled. © 1994 John

ISSN:0006-3592    

DOI:10.1002/bit.260440903

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe production of soluble microbial products (SMP) in anaerobic systems was evaluated using chemostat reactors. Results from steady‐state and tracer experiments with14C‐glucose and14C‐acetate showed that significant amounts of SMP were produced during the acidogenesis of glucose, but that SMP did not accumulate during methanogenesis from acetate. In addition, at a retention time of 40 days, SMP comprised almost all of the effluent COD from the glucose‐fed chemostat. For shorter retention times, as low as 10 days, the SMP concentration remained almost constant, but its significance in the effluent COD was reduced due to the accumulation of intermediate volatile fatty acids. The results from a14C‐tracer experiment in the glucose‐fed chemostat were used to evaluate the importance of including SMP formation and degradation in kinetic modeling of the methanogenic chemostats. Three models were evaluated: a model without SMP production, a model with SMP production but no degradation, and a model with SMP production and degradation, The results of this kinetic analysis indicate that the model that includes SMP production and degradation was the only one able to adequately represent the fate of14C in the tracer experiment. The kinetic parameters were successfully used to predict steady‐state concentrations of SMP and to characterize the formation and degradation characteristics of the SMP. © 1994 John W

ISSN:0006-3592    

DOI:10.1002/bit.260440904

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of acclimatization of microbial populations, compound concentration, and media pH on the biodegradation of low concentration dichloromethane emissions in biofiltration systems was evaluated. Greater than 98% removal efficiency was achieved for dichloromethane at superficial velocities from 1 to 1.5 m3/m3. min (reactor residence times of 1 and 0.7 min, respectively) and inlet concentrations of 3 and 50 ppm Although acclimatization of microbial populations to toluene occurred within 2 weeks of operation start‐up, initial dichloromethane acclimatization took place over a period of 10 weeks. This period was shortened to 10 days when a laboratory grown consortium of dichloromethane degrading organism, isolated from a previously acclimatized column, was introduced into fresh biofilter media. The mixed culture consisted to 12 members, which together were able to degrade dichloromethane at concentrations up to 500 mg/L. Only one member of the consortium was able to degrade dichloromethane were sustained for more than 4 months in a biofilter column receiving an inlet gas stream with 3 ppmvof dichloromethane acidification of the column and resulting decline in performance occurred when a 50‐ppmvinlet concentration was used. A biofilm model incorporating first order biodegradation kinetics provided a good fit to observed concentration profiles, and may prove to be a useful tool for designing biofiltration systems for low concentration VOC emissions. © 1994 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260440905

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of ethanol concentration on cloned gene expression in recombinantSaccharomyces cerevisiaestrain 20B‐12 containing one of two plasmids, pNA3 and pNA7, was investigated in batch cultures. Plasmids pNA3 and pNA7 contain the α‐amylase gene under the control of theSUC2orPGKpromoter, respectively. When the ethanol concentration was controlled at 2 to 5 g/L, the gene expressions were two times higher than those at 20 g/L ethanol. The increase the gene expression by maintaining both the ethanol and glucose concentrations at low levels, a fuzzy ontroller was developed. The concentrations of glucose and ethanol were controlled simultaneously at 0.15 and 2 g/L, respectively, in the production phase using the fuzzy controller in fed‐batch culture. The synthesis of α‐amylase was induced by the low glucose concentration and maintained at a high level of activity by regulating the ethanol concentration at 2 g/L. The secretory α‐amylase was induced by the low glucose concentration and maintained at a high level of activity by regulating the ethanol concentration at 2 g/L. The secretory α‐amylase activities of cells harboring plasmids pNA3 and pNA7 in fed‐batch culture were 175 and 395 U/mL, and their maximal specific activities 7.7 and 12.4 U/mg dry cells, respectively. These values are two to three times higher in activity and three to four times higher in specific activity than those obtained when glucose only was controlled. © 1994 Jo

ISSN:0006-3592    

DOI:10.1002/bit.260440906

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractHydrolysis of microcrystalline cellulose (Avicel) by cellobiohydrolase I and II (CBH I and II) fromTrichoderma reeseihas been studied. Adsorption and synergism of the enzymes were investigated. Experiments were performed at different temperatures and enzyme/substrate ratios using CBH I and CBH II alone and in reconstituted equimolar mixtures. Fast protein liquid chromatography (FPLC) analysis was found to be an accurate and reproducible method to follow the enzyme adsorption. A linear correlation was found between the conversion and the amount of adsorbed enzyme when Avicel was hydrolyzed by increasing amounts of CBH I and/or CBH II. CBH I had lower specific activity compared to CBH II although, over a wide concentration range, more CBH I was adsorbed than CBH II. Synergism between the cellobiohy‐drolases during hydrolysis of the amorphous fraction of Avicel showed a maximum as a function of total enzyme concentration. Synergism measured as a function of bound enzyme showed a continuous increase, which indicates that by decreasing the distance between the two enzymes the synergism is enhanced. The adsorption process for both enzymes was slow. Depending on the enzyme/substrate ratio it took 30–90 min to reach 95% of the equilibrium binding. The amount of bound enzyme decreased with increasing temperature. The two enzymes compete for the adsorption sites but also bind to specific sites. Stronger competition for adsorption sites was shown by CBH I. © 1994 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260440907

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have cloned thekilgene of pMB9 under control of the tightly regulated leftward promoter (pL) of coliphage λ. Three types of plasmids were constructed. In all cases the activity of the λ promoter is controlled by a thermosensitive cl repressor (product of thec/857 gene) supplied form a resident defective prophage or cloned onto a compatible p 15A‐derived plasmid. Induction of the kil protein is brought about by a temperature shift of the culture from 28°C to 42°C. Plasmid pPLc28K1 contains thekilgene including its natural ribosome‐binding site and preceded by a transcription termination site. Using a bacterial strain with antitermination properties (e.g., M5219), periplasmic proteins can upon induction be gradually the growth of the host strain. The second plasmid pPLc321K1, contains thekil‐coding sequence preceded by an engineered ribosome binding site derived from the attenuator of theEscherichia colitryptophan operon. With this plasmid induction of the Kil protein is very rapid and specific release of the periplasmic proteins in essentially complete within 30 min after induction. In a third construct, pcl857K1, thepL‐kilcassette together withc/857allele are present on the same replicon, which is compatible with ColE1‐derived expression vectors. This configuration allows accumulation in the periplasm of cloned gene products, induced by, e.g.,tacortrppromoters at low temperature and subsequent release into the medium following increase of the temperature of the culture. Under repressed conditions (growth at low temperature) all plasmids are perfectly stable in a large number ofE. colistrains tested, also when cultivated on a 20‐L fermentor scale. Controlled, heat‐induced release of periplasmic proteins is highly specific and applicable at relatively high cell densities. The method therefore is an attractive alternative to cumbersome osmotic shock procedures for large‐scale cultures. © 1994

ISSN:0006-3592    

DOI:10.1002/bit.260440908

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA new simple method for the preparation of chemically crosslinked chitosan beads is presented. It consists of the dropwise addition of 2–3% (w/v) low molecular weight chitosan solution containing 2% (w/v) glyoxal in 1% (w/v) tetrasodiumdiphosphate, pH 8.0. Immobilized viable baker's yeast (Saccharomyces cerevisiae) could be obtained via gel entrapment within the new beads when means preventing their direct contact with soluble chitosan were provided, “disguising” the cells until gelation and crosslinking were completed. Such means included cell suspension in castor oil or mixing with carboxymethyl‐cellulose powder. Application of these means was shown to be necessary, as cells exposed to soluble chitosan immediately lost their viability and glycolytic activity. Yeast disguised in castor oil was also protected from bead reinforcement by glutaraldehyde treatment, significantly strengthening bead stability while operating under acidic conditions. This capability was demonstrated by continuous ethanol production by chitosan entrapped yeast. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260440909

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTwo flow parameters are proposed for the analysis of flows that have potential to damage animal cells. They are the state of stress (characterized by the second invariant of the stress tensor) and the flow classification parameterRD(which is related to the possibility of stress relaxation). We consider the flow that occurs when a 1.7‐mm bubble collapses at a liquid interface. Using these two parameters, we show the regions in which the flow is strong in terms of high hydrodynamic stresses and elongation characteristics. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260440910

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractHybridoma batch cultures were extended using feed formulations based on nutrient consumption measured during different batch culture phases when (a) growth but negligible antibody production was taking place; (b) maximum antibody production rate and declining viable cell growth rate were observed. Strategy (a) was the more successful (2.8‐fold compared with 1.8‐fold antibody titer increase) and maintained cell viability for longer. Analysis of the effects of omitting individual amino acids yielded results which were consistent with those from the feeding experiment © 1994 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260440911

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY