摘要:

AbstractA novel process has been used to biodegrade phenol present in an acidic (1MHCI) and salty (5% w/w NaCl) synthetically bioreactor, in which the phenol present in the wastewater is separated from the inorganic components by means of a silicone rubber membrane. Transfer of the phenol from the wastewater and into a biological growth medium allows biodegradation to proceed under controlled conditions which are unaffected by the hostile inorganic composition of the wastewater. At a wastewater flow rate of 18 mL h−1(contact time 6 h), 98.5% of the phenol present in the wastewater at an inlet concentration of 1000 mg  −1was degraded; at a contact time of 1.9 h, 65% of the phenol was degraded. Phenol degradation was accompanied by growth of a biofilm on the membrane tubes and by conversion of approximately 80% of the carbon entering the system to CO2carbon. Analysis of the transport of phenol across the membrane revealed that the major resistance to mass transfer arose in the diffusion of phenol across the silicone rubber membrane. A mathematical model was used to describe the transfer of phenol across the membrane and the subsequent diffusion and reaction of phenol in the biofilm attached to the membrane tube. This analysis showed that (a) the attached biofilm significantly lowers the mass transfer driving force for phenol across the membrane, and (b) oxygen concentration limits the phenol degradation rate in the biofilm. These conclusions from the model are consistent with the experimental results. © 1993 Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260411002

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

年代:1993

数据来源: WILEY

摘要:

AbstractA novel membrane bioreactor has been used for the treatment of an industrially produced wastewater arising in the manufacture of 3‐chloronitrobenzene. This wastewater is not amenable to direct biological treatment without some form pretreatment or dilution, due to the inorganic composition (pH<1, salt concentration 4% w/w) of the wastewater. In the membrane bioreactor, the organic pollutants are first separated from the wastewater by selective membrane permeation, and then biodegraded in the biological growth compartment of the bioreactor. At a wastewater flow rate of 64 mL h−1(corresponding to a contact time of approximately 1.7 hours) over 99% of the 3‐chloronitrobenzene and over 99% of the nitrobenzene in the wastewater were degraded. Degradation of 3‐chloronitrobenzene was accompanied by evolution of chloride ions in a stoichiometric ratio. Both 3‐chloronitrobenzene and nitrobenzene degradation were accompanied by the evolution of carbon dioxide; approximately 80% of the carbon entering the system was oxidized to CO2carbon. Analysis of mass transport across the membrane revealed that 3‐chloronitrobenzene and nitrobenzene are transported more rapidly than phenol. This is explained in terms of a resistances‐in‐series model, which shows phenol transfer to be rate limited by the membrane diffusion step, whereas the chloronitrobenzene and nitrobenzene transfer are rate limited by the liquid film mass transfer. © 1993

ISSN:0006-3592    

DOI:10.1002/bit.260411003

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe stable continuous overproduction of a plasmidencoded protein, β‐lactamase, for at least 50 days byEscherichia coliK‐12, RB791(pKN), with release into the culture medium has been demonstrated in two‐stage chemostats. The second‐stage culture was continuously induced with 0.1 mMIPTG. Continuous expression of β‐lactamase could not be sustained with this strain in a single‐stage chemostat because of cell death and selection forlac−1cells. β‐Lactamase production in the second stage was sensitive to the second‐stage dilution rate and the distribution of the limiting substrate (i.e., glucose) between the first and second stages. The fraction of viable, excreting cells and the average copy number in the induced culture was measurably higher under those conditions of dilution rate and substrate distribution which yielded high β‐lactamase levels. The best operating conditions found at 20°C were a first‐stage dilution rate of 0.12 h−1, a second‐stage dilution rate of 0.03 h−1, and equal glucose feed supplied to each stage. Enzymatically active β‐lactamase was produced at a level of 25% of total cellular protein with 90% excretion yielding 300 mg β‐lactamase/L that was 50% pure

ISSN:0006-3592    

DOI:10.1002/bit.260411004

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

年代:1993

数据来源: WILEY

摘要:

AbstractA phenomenological model has been developed to describe biomass distribution and substrate depletion in porous diatomaceous earth (DE) pellets colonized byPseudomonas aeruginosa.The essential features of the model are diffusion, attachment and detachment to/from pore walls of the biomass, diffusion of substrate within the pellet, and external mass transfer of both substrate and biomass in the bulk fluid of a packed bed containing the pellets. A bench‐scale reactor filled with DE pellets was inoculated withP. aeruginosaand operated in plug flow without recycle using a feed containing glucose as the limiting nutrient. Steady‐state effluent glucose concentrations were measured at various residence times, and biomass distribution within the pellet was measured at the lowest residence time. In the model, microorganism/substrate kinetics and mass transfer characteristics were predicted from the literature. Only the attachment and detachment parameters were treated as unknowns, and were determined by fitting biomass distribution data within the pellets to the mathematical model. The rate‐limiting step in substrate conversion was determined to be internal mass transfer resistance; external mass transfer resistance and microbial kinetic limitations were found to be nearly negligible. Only the outer 5% of the pellets contributed to substrate conversion. © 1993 Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260411005

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

年代:1993

数据来源: WILEY

摘要:

AbstractConcanavalin A, (Con A, MW 26,500/monomer unit) was crosslinked with glutaraldehyde to form soluble, high‐molecular‐weight (larger than MW 300,000) Con A Oligomers. After filtration to remove insoluble and low‐molecular‐weight portions (below 300,000 daltons), the size and molecular‐weight distribution were characterized by laser light scattering and gel‐filtration chromatography. The molecular‐size determined by laser light scattering ranged from 870 to 4070 Å, while the molecular weight determined by gel chromatography ranged from 6 × 105to higher than 2 × 106daltons. The affinity and kinetics of Con A oligomer binding to polysaccharide (glycogen) were evaluated by precipitation test and turbidity development, respectively. The binding with glycogen was strongest at neutral pH and showed similar activity to unmodified Con A molecules. The binding constants of α‐D‐glucose and succinyl‐aminophenyl α‐Dglucopyranoside‐insulin to Con A oligomer were 1.0 × 103M−1and 4.5 × 104M−1, respectively and the binding capacity of the oligomer was nearly 85% to 95% of monomeric Con A. The complexes of saccharides and soluble Con A oligomer were stable for at le

ISSN:0006-3592    

DOI:10.1002/bit.260411006

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

年代:1993

数据来源: WILEY

摘要:

AbstractA split‐stream flow‐injection analysis system is described for simultaneous determination of glucose andL‐glutamine in serum‐free hybridoma bioprocesses media. Amperometric measurement of glucose is based on anodic oxidation of hydrogen peroxide produced by immobilized glucose oxidase within a triple layer membrane of an integrated flow‐through glucose‐selective biosensor. Determination ofL‐glutamine is based on quantitating ammonium ions produced in a flow‐through enzymes reactor containing immobilized glutaminase enzyme, and subsequent downstream potentiometric detection of these ions by a nonacting‐based ion‐selective polymer membrane electrode. Endogenous potassium and ammonium ion interference in theL‐glutamine determination are eliminated by using a novel in‐line tubular cation‐exchange membrane unit to exchange these interferent species for cations undetectable by the membrane electrode. The first generation split‐steam flow‐injections system can assay 12 samples/h using direct injections of 50 μL of media samples, with linear responses to glucose in the range of 0.03 to 30mM, and log‐linear response toL‐glutamine from 0.

ISSN:0006-3592    

DOI:10.1002/bit.260411007

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

年代:1993

数据来源: WILEY

摘要:

AbstractBasic issues in the culture of the extremely thermophilic archaeon,Methanothermus fervidus,have been investigated, including culture medium formulation, substrate yield and product yield coefficient, growth rate and stoichiometry, and H2uptake kinetics. The pH optimum for growth of this organism was estimated at 6.9. Growth medium buffered with PIPES instead of bicarbonate supported both increased growth rate and maximum biomass concentration. Substitution of titanium(III) citrate for the reducing agent sodium sulfide improved culture performance as well. However, independent adjustment of iron and nickel concentrations from 11 to 111 μM, respectively, and carbon dioxide partial pressure from 5 to 20 psia did not impact the culture ofM. fervidussignificantly. An elemental balance approach was utilized to aid in design of a defined medium to support growth to a target maximum biomass concentration of at least 1.0 g dry wt/L. The growth of this organism was limited by H2availability in this reformulated culture medium. The maximum growth rate and biomass concentration achieved in anaerobic vials with the defined medium was 0.16 h−1and 0.74 g dry wt/L, respectively. This maximum biomass concentration was a 72% improvement over that obtained with a literature‐based defined medium. The Monod parameter,Ks, with H2as limiting substrate, was estimated at 1.1 ± 0.4 psia (55 ± 20 μM in the broth), based on a H2consumption study. Representative values for the substrate yield,Y X/CO 2, and product yield coefficient,Y CH 4/X, were determined experimentally to be 1.78 ± 0.04 g dry wt/mol CO2, and 0.52 ± 0.01 mol CH4/g dry wt, respectively. A bench‐scale fermentation system suitable for the culture of extremely thermophilic anaerobes was designed and constructed and proved effective for the culture ofM. fervidus. ©

ISSN:0006-3592    

DOI:10.1002/bit.260411008

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

年代:1993

数据来源: WILEY

摘要:

AbstractA laboratory‐scale multiphase hollow fiber membrane reactor was employed to investigate the lipase‐catalyzed enzymatic resolution of racemic glycidyl butyrate. A mathematical formulation was feveloped to simulate the performance of this system. Model parameters were determined independently (except the effective rate constant, ks) and incorporated in the model simulations. In this study, two modes of operation are considered:subtractive resolution,in which the unreacted substrate is recovered in the organic stream; andproduct recovery,where the optically pure product of theenzymaticreaction is recovered in the aqueous stream. Good agreement was obtained between theoretical predictions and experimental results under a variety of conditions. The effect of mass transport limitations on the performance of this system was investigated. An increase in enzyme loading resulted in a higher Thiele modulus due to an elevated rate constant as well as a concomitant decrease in the effective diffusivity. Optical purity decreased in both subtractive resolution and product recovery at higher Thiele modulus with the effect being more pronounced in the product recovery mode. Finally, normalized plots were established to describe the effect of enzyme immobilization on both the effective enzymes activity and effective diffusivity. © 1993 Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260411009

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

年代:1993

数据来源: WILEY

摘要:

AbstractA novel technique for affinity precipitation has been developed in which multimeric target proteins are precipitated as a result of network formation by polymer‐conjugated ligands (polyligands). A polyligand precipitant for avidin was synthesized by conjugation of biotin to a polyacrylamide‐based backbone. The effects of mixing conditions, ligand substitution frequency, and molecular weight on affinity precipitation were examined using the biotin‐PAAm precipitant. Biotin was replaced by iminobiotin to study the effect of the ligand‐protein dissociation constant o affinity precipitation. The iminobiotin‐PAAm precipitant was also used to examine the reversibility of the precipitation and recovery of the target protein after precipitation. © 1993 Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260411010

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe recovery of proteins from yeast cell debris suspension was investigated using a vortex mixing technique based on the combination of oscillatory flow and a baffled flat‐sheet microfiltration system. For this system, increased protein transmission was obtained through the use of low transmembrane pressures and the preincubation of the yeast cell debris feed suspension at 30°C. Furthermore, a plateau in the flux‐time curve was observed. In the absence of baffles and pulsations, preincubation had a little effect. © 1993 Wiley&Sons

ISSN:0006-3592    

DOI:10.1002/bit.260411011

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

年代:1993

数据来源: WILEY