摘要:

AbstractAffinity membranes for the treatment of solutions containing amino acids were obtained via lithiating polysulfone that was subsequently converted with glycidylether. From this polymer asymmetric ultrafiltration membranes were cast. The membranes were reacted with iminodiacetic acid yielding membranes fitted out with bidentate chelates. The same reaction path was applied to commercially available symmetric microfiltration membranes. The chelate‐bearing membranes were complexed with Cu, Ni, and Zn ions. For the experiments with amino acids only the Cu‐complexed membranes were used. The complexation constants for histidine and tryptophan for six different membranes were determined. Because of the affinity of these two amino acids for the complexed Cu ions, they could easily be separated from solutions containing amino acids such as alanine, glycine, and valine. Also, concentrating very dilute amino acid solutions was carried out successfully. © 1995 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260460602

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe first large‐scale production of 7‐aminocephalosporanic acid (7ACA) from cephalosporin C (CPC) using a wholly enzymatic synthesis method is reported here. We produced 7ACA from CPC in as high a molar yield as 85% using the immobilized enzymes D‐amino acid oxidase (D‐AOD) and glutaryl‐7‐ACA acylase (GL‐acylase). In the first reactor, CPC is converted to keto‐adipyl‐7‐aminocephalosporanic acid (keto‐7ACA) using an immobilized D‐AOD isolated from a yeast,Trigonopsis variabilis. The keto‐7ACA is then spontaneously converted to glutaryl‐7‐aminocephalosporanic acid (GL‐7ACA) via a chemical reaction with hydrogen peroxide. The hydrogen peroxide is also a product of the D‐AOD reaction. Near quantitative conversion of the keto‐7ACA to GL‐7ACA was observed. The second reactor converts GL‐7ACA to 7ACA using an immobilized GL‐acylase, which was isolated from a reconbinantEscherichia coli. The final 7ACA crystalline product is a high quality product. The reactions are conducted under very mild aqueous conditions: pH 8.0 and 20° to 25°C. The production of desacetyl side products is minimal. This process is currently being implemented on an industrial scale t

ISSN:0006-3592    

DOI:10.1002/bit.260460603

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe design, construction, and characterization of a prototype‐regenerable glucose biosensor based on the reversible immobilization of glucose oxidase (GOx) using cellulose binding domain (CBD) technology is described. GOx, chemically linked to CBD, is immobilized by binding to a cellulose matrix on the sensor‐indicating electode. Enzyme immobilization can be reversed by perfusing the cellulose matrix with a suitable eluting solution. An autocavable sensor membrane system is employed which is shown to be practical for use in real microbial fermentations. The prototype glucose biosensor was used without failure or deterioration during fed‐batch fermentations ofEscherichia colireaching a maximum cell density of 85 g (dry weight)/L. Medium glucose concentration based on sensor output correlated closely with off‐line glucose analysis and was controlled manually at 0.44 ± 0.2 g/L for 2 h based on glucose sensor output. The sensor enzyme component could be eluted and replaced without interrupting the fermentation. To our knowledge, no other in situ biosensor has been used for such an extended period of time in such a high‐cell‐density fermentation. © 1995 John Wi

ISSN:0006-3592    

DOI:10.1002/bit.260460604

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

年代:1995

数据来源: WILEY

摘要:

AbstractIt has previously been found tht hybridoma cells undr hyuerosmotic stress produce higher amounts of antibody. This study indentified the cellular processes and mechanisms that occur during this event. In studies fo hybridomas adpated toosmolarities ranging between 300 and 450 mOsm (uusing NaCl), antibody production increased to a saturation level while cell growth decreased progressively. At 500 mOsm, lower, cell numbers and markedly decreaased productivity resulted. Sucrose and KCl were found to induce similar trends, except to different extents.Several important change in cellulaes in cellular responses were onsserved. Elevation of osmnolarity with NaCl from 300 to 350 mOsm causes an increase of zwiterionic amino acid upatake, which, occurredvia Na+‐dependent transport systems. In particuar, systedm A was enhanced by 1.86‐fold, but noenhancement was observed for Na+‐independent transport systems, In addition, amino acids reactive with Na+‐dependent transport systems were onserved to be abundant within osmotically stressed hybridomas in the middle and dlate exponentoial statges. Sucroses ans Kcl caused similar uptake effects, but to a laeeser degree, as long as sodium ions were present in solution.Specific consumption rates fo glucose and glutamine incresase by 19% and 20%, respectively, under high osmolarity treatment. Thewse increases were confirmed by the 5% to 10% increase in cellular metabolic acitivity. At 350 mOsm, growth rate was slower, compared with the 300‐mOsm culture, which was reflected by thelower DNA conetr4ation. Stressed cultures contained enhanced leyls of tatal RNA content could in turn increase the translation rates of proteins. This was reflected in the accumulation of both dry cell weight and total cellular protein at linear rates of 0.42 μG/106cells/mOsm and 0.21 μg/106cells/mOmsm, respectively, with increasing osmolarty between 300 and 450 mOsm.Overall, hybridoms increased their metabolic activities and amino acids uptake via the Na+‐dependent symports to compensate for teh osmotically elevated external environment. These effects contribute directly and indirectly tothe increased cell mass consisting of a larger pool of amono acids, RNA, cellular proteins, and seecreted antibody produt. © 1995 John W

ISSN:0006-3592    

DOI:10.1002/bit.260460605

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of different short‐term controlled cell culture conditions on the product quality of a genetically engineered human interleukin‐2 N‐glycosylation variant protein expressed from a baby hamster kidney cell line (BHK‐21) has been investigated. A perfused 2‐L stirred tank reactor was used. Products purified from the culture supernatant of cells grown under experimentally initiated nutrient limitations (glucose, amino acids, pO2) were characterized by their HPLC‐elution profile, SDS‐PAGE and western blotting, amino acid sequencing as well as for their N‐linked carbohydrates, using “HPAEC‐PAD fingerprinting” and methylation analysis. The glycoprotein products secreted from cells under the different culture conditions (kept for 24 h, after an adaption time period of 48 h) showed an almost identical oligosaccharide pattern. By contrast, short‐term changes of the culture condition led to considerable differences in the ratio of glycosylated to unglycosylated protein forms. Significant amounts of NH2‐terminally truncated polypeptide forms were observed. They lacked proponderantly the first two amino acids; however, under certain culture conditions forms lacking up to eight NH2‐terminal amino acids were detected.

ISSN:0006-3592    

DOI:10.1002/bit.260460606

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

年代:1995

数据来源: WILEY

摘要:

AbstractAn original reaction system (the phase separative reaction system) has been designed for derivatizing native lignins to highly phenolic, functional polymers. This system is composed of a phenol derivative and concentrated acid, which are not miscible at room temperature. The key point of the lignin functionalization process, including the phase separative system, is that lignin and carbohdrates, which are totally different in structures and reactivitie, are modified individually in the different phases: lignin is present in the organic phase and carbohydrates in the aqueous phase. Through the process, lignin was modified selectively at Cα‐positions of side chains, the most reactive sites, to give highly phenolic, light‐colored, diphenylmethane‐type materials which still retained original interunit linkages formed by the dehydrogenative polymerization during the biosynthesis. The carbohydrates were swollen, followed by partial hydrolysis and dissolution in the acid solution, resulting in the perfect decomposition of interpenetrating polymer network structures in the cell wall. Therefore, the functionalization of lignin and the separation of resulting lignin from carbohydrates were quickly achieved at room temperature, independent of wood species. This process would be a powerful tool for estimating strutures and reactivities of lignins as well as the functionalization of lignins, because of the selective structural modifications. © 1995 John Wiley&So

ISSN:0006-3592    

DOI:10.1002/bit.260460607

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of biofilm areal cell density, species composition, and the presence of abiotic particles on the disinfection and removal of bacterial biofilms by monochloramine was investigated. Mono‐ and binary population biofilms ofPseudomonas aeruginosaandKlebsiella pneumoniaewere grown on stainless‐steel slides in a continuous flow annular reactor. Biofilms were treated in the reactor with a pulse/step dose of 4 mg/L monochloramine for 2 h. Biofilm samples were disaggregated and assayed for colony formation on R2A agar and for total cell numbers by acridine orange direct counts. These data were used to determine apparent first order rate coefficients for the processes of disinfection and detachment. Disinfection rate coefficients exceeded detachment rate coefficients by as much as an order of magnitude and the two coefficients were poorly correlated (r= 0.272). The overall decay rate coefficient (disinfection plus detachment) depended strongly on the initial biofilm areal cell density. It displayed a parabolic dependence on cell density with a maximum near 108cfu/cm2. This result points to multiple factors influencing biofilm susceptibility to antimicrobial challenge. Decay rates ofK. pneumoniaemeasured in binary population biofilms were comparable with those measured in monopopulation biofilms (p= 0.61).P. aeruginosadecayed more slowly in biofilsm dominated byK. pneumoniae(p= 0.028), indicating some interaction between species. The presence of kaolin and calcium carbonate particles in the biofilm reduced disinfection efficacy. © 1995 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260460608

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn liquid culture, filamentous organisms often grow in the form of pellets. Growth result in an increase in radius, whereas shear forces result in release of hyphal fragments which act as centers for further pellet growth and development. A previously published model for pellet growth of filamentous microorganisms has been examined and is found to be unstable for certain parameter values. This instability has been identified as being due to inaccuracies in estimating the numbers of fragments which seed the pellet population. A revised model has been formulated, based on similar premises, but adopting a finite element approach. This considers the population of pellets to be distributed in a range of size classes. Growth results in movement to classes of increasing pellet size, while fragments enter the smallest size class, from which they grow to form further pellets. The revised model is stable and predicts changes in the distribution of pellet sizes within a population growing in liquid batch culture. It considers pellet growth and death, with fragmentation providing new centers of growth within the pellet population, and predicts the effects of shear forces on pellet growth and size distribution. Predictions of pellet size distributions are tested using previously published data on the growth of fungal pellets and further predictions are generated which are suitable for experimental testing using cultures of filamentous fungi or actinomycetes. © 1995 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260460609

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

年代:1995

数据来源: WILEY

摘要:

AbstractCarrot somatic embryos were encapsulated in alginate gel beads. To improve the quality of a “synthetic seed” coating, the rheology and dehydration properties of different matrices were tested. By increasing alginate and CaCl2concentrations, additional mineral elements were shown to increase resistance to rupture, and to depress the germination of somatic embryos. A polysaccharide addition was found to slow the alginate matrix dehydration; alginate‐gellan gum and alginate‐kaolin matrices could preserve the viability of somatic embryos at low relative humidities (30% to 35% germinations at 50% relative humidity) to a greater extent than other matrices. © 1995 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260460610

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

年代:1995

数据来源: WILEY

摘要:

AbstractA hybridoma cell line was cultivated in fed‐batch cultures using a low‐protein, serum‐free medium. On‐line oxygen uptake rate (OUR) measurement was used to adjust the nutrient feeding rate based on glucose consumption, which was estimated on‐line using the stoichiometric relations between glucose and oxygen consumption. Through on‐line control of the nutrient feeding rate, not only sufficients were supplied for cell growth and antibody production, but also the concentrations of glucose and other important nutrients such as amino acids were maintained at low levels during the cell growth phase. During the cultivation, cell metabolism changed from high lactate production and low oxygen consumption to low lactate production and high oxygen consumption. As a result the accumulation of lactate was reduced and the growth phase was extended. In comparison with the batch cultures, in which cells reached a concentration of approximately 2 × 106cells/mL, a very high concentration of 1.36 × 107cells/mL with a high cell viability (>90%) was achieved in the fed‐batch culture. By considering the consumption of glucose and amino acids, as well as the production of cell mass, metabolites, and antibodies, a well‐closed material balance was established. Our results demonstrate the value of coupling on‐line OUR measurement and the stoichiometric realations for dynamic nutrient feeding in high cell concentration fed batch cultures. © 1995

ISSN:0006-3592    

DOI:10.1002/bit.260460611

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

年代:1995

数据来源: WILEY