摘要:

AbstractLiquid–liquid extraction and membrane separation are well‐known separation method of extensive industrial application. Their incorporation into liquid membranes has the potential of several advantages, some of which are of particular interest for the recovery of carboxylic and amino acids: selectivities higher than those attainable by current separation methods, saving on energy costs for final concentration of separated products, high fluxes, compact installation, and low capital and operation costs. Stability of the liquid advantages, can be secured by utilizing extractant blocking polymeric membranes, Applicability, process consideration, and economic implications for recovery for carboxylic and amino acids by various extractant/membrane combinations are discussed. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410302

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

年代:1993

数据来源: WILEY

摘要:

AbstractWhen a dissolved oxygen (DO) probe is submerged in an air‐saturated cell culture medium the thickness of the liquid film that exists outside the membrane of a DO probe changes with hydrodynamic shear. The response of the DO probe thus varies with the hydrodynamic shear environment near the DO probe in cell culture reactors. The thickness of the liquid film was estimated by using a three‐layer model, which describes the flow of DO molecules through the liquid layer, the membrane, and the electrolyte, to the cathode of a DO probe. According to the three‐layer model, the current output of the DO probe was a strong function of thickness of the liquid film outside the membrane of the DO probe. A correlation between shear rates on the surface of the probe and the DO saturation reading was obtained by using two concentric cylinders with a rotating inner cylinder. This correlation was then used to characterize the local hydrodynamic shear environment in a cell culture reactor. © 1993 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260410303

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

年代:1993

数据来源: WILEY

摘要:

AbstractAs an alternative to the current disposal technologies for waste sulfuric acid, a new combination of recycling processes was developed. The strong acid (H2SO4) is biologically converted with the weak acid (CH3COOH) into two volatile weak acids (H2S, H2CO3) by sulfate‐reducing bacteria. The transformation is possible without prior neutralization of the sulfuric acid. The microbially mediated transformation can be followed by physiochemical processes for the further conversion of the H2S.The reduction of sulfate to H2S is carried out under carbon‐limited conditions at pH 7.5 to 8.5. A fixed‐bed biofilm column reactor is used in conjunction with a separate gas‐stripping column which was installed in the recycle stream. Sulfate, total sulfide, and the carbon substrate (in most cases acetate) were determined quantitatively. H2S and CO2are continually removed by stripping with N2. Optimal removal is achieved under pH conditions which are adjusted to values below thepKa‐values of the acids. The H2S concentration in the stripped gas was 2% to 8% (v/v) if H2SO4and CH3COOH are fed to the recycle stream just before the stripping column.Microbiol conversion rates of 65 g of sulfate reduced per liter of bioreactor volume per day are achieved and bacterial conversion efficiencies for sulfate of more than 95% can be maintained if the concentration of undissociated H2S is kept below 40 to 50 mg/L. Porous glass spheres, lava beads, and polyurethane pellets are useful matrices for the attachment of the bacterial biomass. Theoretical aspects and the dependence of the overall conversion performance on selected process parameters are illustrated in the Appendix to this article. © 1993 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260410304

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

年代:1993

数据来源: WILEY

摘要:

AbstractAmong amino acids screened for their potential to relieve wild and recombinantEscherichia colifrom the negative effects of acetic acid, glycine, and methionine showed a sparing effect. In the presence of 2 g/L of acetic acid, addition of 0.5 g/L of glycine or methionine resulted in either a complete recovery or a further enhancement in the specific growth rate, while the enhancement was significant but not fully complete in the presence of 4 g/L of acetic acid. The addition of 0.5 g/L of methionine alleviated the negative effect of acetic acid on recombinantE. Coligrowth to produce more β‐lactamase, which was encoded by plasmid pUC18. In continuous fermentation the methionine effect on recombinant.E. colimetabolism depended on dilution rate; at high dilution rates, above 0.4 h−1, the methionine addition enhanced β‐lactamase production and reduced acetic acid formation, while at low dilution rates, below 0.3 h−1, the effect was reversed. In def‐batch fermentation with wild‐typeE. Coli, cell growth rate and cell yield from glucose were enhanced with methionine addition, while the acetic acid concentration reached over 4 g/L. © 1993 John W

ISSN:0006-3592    

DOI:10.1002/bit.260410305

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of plasmid‐mediated metabolic burden of on the expression of the host genes and its consequences on the plasmid maintenance were studied in carbon‐limited chemostat culture ofEscherichia coli1EA(pBR322) subject to selection for strains overproducing chromosomally coded ribitol dehydrogenase. The chemostat population became rapidly heterogeneous and the competition among evolved strains was found to be crucial for the kinetics of the plasmid loss from the culture. The selective disadvantages in growth rate associated with plasmid carriage in the parent‐like and ribitol dehydrogenase‐overproducing strains was estimated. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260410306

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

年代:1993

数据来源: WILEY

摘要:

AbstractImmobilization offers several intrinsic advantages over free suspension cultures for the production of monoclonal antibodies. An important advantage of immobilization is the improved specific monoclonal antibody (MAb) productivity (qMAb) that can be obtained. However, there are conflicting reports in the literature on the enhancement of the qMAbwith immobilization. The discrepancies between these reports can be attributed to the different to either the cultivation methods used for immobilized cell or to difference between the cell lines used in the various studies. We show that these differences may be attributed to the different cultivation methods used for one model hybridoma cell line. S3H5/ϒ2bA2 hybridoma cells entrapped in different sizes of calcium alginate beads were cultivated in both T‐ and spinner flasks in order to determine whether cultivation methods (T‐ and spinner flasks) and bead size influence the qMAbFree‐suspended cell cultures inoculated with cells recovered from alginate beads were also carried out in order to determine whether changes in the qMabof the entrapped cells are reversible.The cultivation methods was found to influence significantly the qMAbof the entrapped cells. When the entrapped cells in 1‐mn diameter beads were cultivated in T‐flasks, the qMAbwas not increased by 200% as previously observed in an entrapped cell culture using 1‐mm‐diameter alginate beads in spinner flasks. The qMAbof the entrapped cell was approximately 58% higher than that of the free‐suspended cells in a control experiment. Unlike the cultivation method, the bead size in the range of 1‐ to 3‐mm diameter did not significantly influence the qMAb, regardless of cultivations methods. The changes in qMAbof an entrapped cells were reversible. When the free‐suspended cells recovered from the T‐ and spinner flasks were sub‐cultured in T‐ and spinner flasks enhanced qMAbof the entrapped cells in both cases decreased to the level of the free‐suspended cell in a control experiments. Taken together, these results shows that the method of cultivation of hybridoma cells immobilized in alginate beads determines the extent of enhancement of the qMA

ISSN:0006-3592    

DOI:10.1002/bit.260410307

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

年代:1993

数据来源: WILEY

摘要:

AbstractGas antisolvent (GAS) expansion of dimethylsulfoxide (DMSO) andN,N‐dimethylformamide (DMFA) solutions with supercritical carbon dioxide was used to produce biologically active powders of insulin. Powders with 90% of the particles smaller than 4 μm and 10% smaller than 1 μm were obtained under all conditions tested when the process was operated continuously, with small liquid droplets sprayed into a flowing supercritical continuum. Slow pressurization of the stagnant protein solution resulted in larger particles. In vivo tests on rats revealed no differences between the biological activity of processed and unprocessed insulin, GAS processing of organic solution appears to be a reliable and effective method for the production of dry, biologically active microparticulate powders of peptides and proteins. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410308

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe startup of anaerobic fluidized bed reactors, which use Manville R‐633 beads as the growth support media, acetate enriched bacterial culture as the inoculum, and acetic acid as the sole substrate, is studied. Tow startup strategies are evaluated: one based on maximum and stable substrate utilization and another based on maximum substrate loading controlled by reactor pH. The startup process is characterized using a number of operational parameters.The reactors again excellent total organic carbon (TOC) removal (i.e.,>97% at a feed concentration of 5000 mg TOC/L) and stable methane production (i.e., 0.90 L CH4/g TOC, where TOCris TOC removed) at a early stage of the startup process, regardless of the strategies applied. The loading can be increased rapidly without the danger of being overloaded. Significant losses of growth support media and biomass caused by gas effervescence at higher loadings limits the maximum loading that can be safely applied during startup process.A high reactor immobilized biomass inventory is achievable using the porous growth support media (e.g., Manville 633 beads). A rapid increase in loading creates a substrate rich environment that yields more viable reactor biomass. Both substrate utilization rate (batch and continuous) and immobilized biomass inventory stabilize concomitantly at the late stage of the startup process, indicating the attainment of steady‐state conditions in reactors. Therefore, they are better parameters that TOC removal and methane production for characterizing the entire startup process of aerobic fluidized bed reactor.The strategy based on maximum substrate loading controlled by reactor pH significantly shortens the startup time. In this case, the reactor attains steady‐state conditions approximately 140 days after startup. On the other hand, a startup time of 200 days is required when the strategy based maximum substrate utilization is adopted. © 1993 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260410309

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

年代:1993

数据来源: WILEY

摘要:

AbstractA stimulus–response tracer technique has been used to characterize packed beds of untreated, as well as acid prehydrolyzed, and enzymatically hydrolyzed aspen wood chips. Glucose was used as the tracer. Bulk liquid phase dispersion, interphase mass transfer, and intraparticle diffusion coefficients were determined for these materials as well as effective porosities and tortuosities. The untreated and prehydrolyzed aspen wood chips were found to have effective coid fractions of ca. 0.8, while the enzymatically hydrolyzed wood chips exhibited a void fraction of 0.37. Intraparticle diffusion was approximately twice as rapid in the prehydrolyzed and enzymatically hydrolyzed wood chips as in the untreated wood chips. Also, under the current experimental conditions, intraparticle diffusional transport resistance accounted for roughly half of the total tracer pulse dispersion. It is demonstrated that stimulus‐response tracer techniques can be useful and convenient probes for beds of lignocellulosic, or other conversion and/or treatment. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410310

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

年代:1993

数据来源: WILEY

摘要:

AbstractA mathematical model for the sedimentation velocity in an inclined parallel plate sedimenter is proposed. The parameters of the alcoholic fermentation broth (cell density ofSaccharomyces cerevisiae, density of the fermentation medium, viscosity of the broth at various alcohol and biomass contents) were determined experimentally. The sedimentation velocities were predicted under the various operational conditions and parameters, both of the broth (the alcohol concentration and cell content) and the sedimenter prototype (length, distance between the plates, and slope). The proposed model for the sedimentation velocity presented a good correlation with the experimental results of continuous sedimentation. These sedimenter prototypes were assembled and tested for efficiency of separation of yeast cell under conditions considered for interest for continuous alcoholic fermentation. A selective filter for the overflow composed of calcium alginate gel improved operation. A high operational stability, high separation efficiency (over 98%), and adequate settler residence times (about 20 min) were attained. The operational results permitted the operation of continuous alcoholic fermentation with cellular recycling effected exclusively by gravitational sedimentation, this characterizing a process of enormous industrial interest because of the operational simplicity and low operational and maintenance costs. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410311

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

年代:1993

数据来源: WILEY