摘要:

AbstractIn order to better understand the high plasmid stability in immobilized recombinantE. colicells, the effects of dilution rate on the pTG201 plasmid stability, the copy number, and the catechol 2,3‐dioxygenase (encoded byXyIEgene) production were, at first, studied in freeE. coliW3101 continuous cultures in minimal media. It was found that decreasing specific growth rate increased the plasmid copy number and the catechol 2,3‐dioxygenase activity but the stability decreased. In continuous culture with immobilized cells, an increase was shown in plasmid copy number and catechol 2,3‐dioxygenase activity probably due to the distribution of growth in the gel beads. Besides mechanical properties of gel beads which may allow limited cell divisions, the increase in plasmid copy number is involved in enhanced plasmid stability in immobilized cells. In the same way, an experiment conducted in LB medium dealing with competition between pTG201‐free and pTG201‐containingE. coliB cells was described. It was shown that the competition was not more pronounced in gel bead compared to a free system. The effects of nutritional limitations on pTG201 plasmid stability and catechol 2,3‐dioxygenase activity during chemostat cultivations in free and immobilizedE. coliB cells were also investigated. It was found that immobilization of cells increased the stability of pTG201 even under glucose, nitrogen, or phosphate limited cultures. However in the case of magnesium depleted culture, pTG201 was shown to be relatively instable and a decrease in viable cell number during the immobilized continuous culture was observed. By contrast to the free system, the catechol 2,3‐dioxygenase activity increased in immobilized cells under all culture co

ISSN:0006-3592    

DOI:10.1002/bit.260330702

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

年代:1989

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260330703

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

年代:1989

数据来源: WILEY

摘要:

AbstractFollowing an effective accumulation of cobalt by nonliving algal biomass ofAscophyllum nodosum, the desorption release of the metal from the biosorbent was examined using H2SO4, HCl, NH4OH, KHCO3, EDTA, KSCN, KCl, and CaCl2solutions. The solution of CaCl2(0.05M) in HCl appeared to be the best eluant capable of desorbing more than 96% of the sequestered cobalt at the optimum pH 2–3. The optimum solid‐to‐liquid ratio was more than 10 with the cobalt reuptake capacity of the biosorbent undiminished. The effect of temperature on the elution process and the elution rate was not significant up to 60°C. The infrared (IR) spectra of the native and the eluted biomass did not show significant differences. The electron micrographs of the algal biomass taken after washing it with the CaCl2(0.1M) eluant solution indicated no damage to the cells and cell walls, while strong acid, alkaline, and KSCN treatment resulted in some changes in the cellular structure. The kinetics of the cobalt stripping process was quite rapid. The required contact time for the complete metal removal from the biomass was shorter than 2 h, even for the highest levels of cobalt initially deposited on the b

ISSN:0006-3592    

DOI:10.1002/bit.260330704

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

年代:1989

数据来源: WILEY

摘要:

AbstractNonliving biomass of the common seaweedAscophyllum nodosumis capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co2+/g. Successful desorption of cobalt from the biomass by acidic CaCl2solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of cobalt. Chemical and instrumental analysis including electron microscopy, infrared (IR) spectroscopy, X‐ray dispersion and diffraction analysis provided supporting evidence that the biosorption mechanism involves predominantly ion exchange. Alginates of the cell wall (‐COOH groups) play an important role in cobalt binding. Coordination and sorption in the cell wall structure occur simultaneously and rapidly whereas penetration of cobalt into the cell occurs at a lower r

ISSN:0006-3592    

DOI:10.1002/bit.260330705

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

年代:1989

数据来源: WILEY

摘要:

AbstractTwo strains ofPseudomonasable to grow on phenol orp‐nitrophenol (PNP) were isolated from sewage.Pseudomonassp. PN101 mineralized and formed nitrite from PNP but did not mineralize phenol, andPseudomonassp. PH111 mineralized phenol but not PNP. Phenol increased the lag period beforePseudomonassp. PN101 grew on and mineralized PNP, but this toxicity was reduced by inoculation of the medium withPseudomonassp. PH111. PNP inhibited growth ofPseudomonassp. PH111 and slightly increased the length of the acclimation period for the mineralization of phenol by the bacterium. Inoculation ofPseudomonassp. PN101 into solutions containing PNP and phenol increased the lag period prior to growth ofPseudomonassp. PH111 on phenol and markedly lengthened the lag period for its mineralization of phenol. Coinciding with this delay in the onset of phenol degradation was the accumulation of an organic compound formed from PNP byPseudomonassp. PN101. This compound was not mineralized by the phenol‐degrading bacterium. The data suggest that bacteria may interact during the decomposition of chemical mixtures by destroying or by forming toxins that affect the biodegradation of individual components of those mixtu

ISSN:0006-3592    

DOI:10.1002/bit.260330706

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of hydrogen acceptors on the kinetic parameters ofD‐xylose fermentation under anaerobic conditions was studied in a transient culture of immobilizedPachysolen tannophiluscells. Addition of oxygen to a steady‐state culture resulted in a rapid increase (up to fivefold) in the rates of ethanol production andD‐xylose uptake, but the rate of xylitol production was unaffected. Furthermore, the molar ethanol yield increased from 0.97 to 1.43 in the presence of oxygen. The moles of ethanol produced per moles of oxygen utilized were considerably greater than would be predicted from the stoichiometry ofD‐xylose fermentation, which suggests that the organism required oxygen for other functions in addition to its role as a hydrogen acceptor inD‐xylose metabolism. When the artificial hydrogen acceptors acetone, acetaldehyde, and acetoin were added to the culture, the rate of ethanol production increased while the xylitol production rate decreased but the rate of xylose uptake was unaffected. The molar ethanol yields increased from 1.03 to 1.63, 1.43, and 1.24 upon addition of acetaldehyde, acetone, and acetoin, respectively, at the expense of the molar xylitol yields. The hydrogen acceptors sodium acetate, methylene blue, benzyl viologen, phenazine methosulfate, indigo carmine, and tetrazolium chloride had no effect on ethanol p

ISSN:0006-3592    

DOI:10.1002/bit.260330707

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe stability of immobilized maltotetraose (G4)‐forming amylase (1,4‐α‐D‐glucan maltoteraohydrolase, EC 3.2.1.60) fromPseudomonas stutzeriwas investigated in both batch and continous processes. The inactivation process of the immobilized enzyme seemed to obey first‐order kinetics, and the immobilized enzyme became more stable when coexisting with 20–30 wt % substrate and calcium ions. From intensive studies on the operational stability in the continuous process, the apparent half‐life of G4productivity in a constant‐flow system was mainly affected by the reaction temperature, substrate concentration, and initial immobilized enzyme activity. A new factor, immobilized enzyme stability factorfs, was proposed to evaluate the half‐life of the immobil

ISSN:0006-3592    

DOI:10.1002/bit.260330708

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

年代:1989

数据来源: WILEY

摘要:

AbstractA forced‐flow enzyme membrane reactor system for sucrose inversion was investigated using three ceramic membranes having different pore sizes. Invertase was immobilized chemically to the inner surface of a ceramic membrane activated by a silane—glutaraldehyde technique. With the cross‐flow filtration of sucrose solution, the reaction rate was a function of the permeate flux, easily controlled by pressure. Using 0.5 μm support pore size of membrane, the volumetric productivity obtained was 10 times higher than that in a reported immobilized enzyme column reactor, with a short residence time of 5 s and 100% conversion of the sucrose inv

ISSN:0006-3592    

DOI:10.1002/bit.260330709

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

年代:1989

数据来源: WILEY

摘要:

AbstractAnimal cells are exposed to turbulent fluid flow in many cell culture processes. If the turbulence in the flow is sufficiently strong, the cells will be damaged or killed by fluid‐mechanical forces. Through an increase in viscosity, the turbulence can be damped and the hydro‐dynamic damage can be reduced. In this article, new experimental results are presented which illustrate the protective effect of thickening agents. The results follow the prediction of a model based on Kolmogorov's theory of universal equilibrium in turbulent flow fie

ISSN:0006-3592    

DOI:10.1002/bit.260330710

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe hydrolysis of lactose using immobilized β‐galactosidase (fromAspergillus niger) on phenol–formaldehyde resin was studied at temperatures between 8 and 60°C and initial lactose concentrations ranging from 2.5 to 20.0%. A model involving enzyme–galactose complex similar to Michaelis–Menten kinetics with competitive product (galactose) inhibition is suitable to describe the lactose hydrolysis reaction. A small degree of lack of fit between the model and the data was found to be due to the formation of oligosaccharides. Thermal deactivation of lactase follows first‐order reaction mechanism. The effect of temperature on the reaction and the deactivation rate constants follows the Arrhenius relationship. The Oligosaccharide formation was not significantly affected by the temperature when the initial lactose concentration was 5%. A design equation for the plug‐flow immobilized lactase reactor was developed from the reaction and the deactivation kinetics and was used to find the optimal operating temperature. The optimal temperature was found to be dependent on the operating time but not on the lactose concentration or the conversion. The optimal operating temperature is 60°C when operating time is short but is close to 35°C for a long operating time. A preliminary economic analysis indicates that the optimal operating temperature is 43, 38.5, and 33°C when the operating time is 300 days, 1000 days, and infini

ISSN:0006-3592    

DOI:10.1002/bit.260330711

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

年代:1989

数据来源: WILEY