摘要:

AbstractThe quasi‐steady‐state (QSS )controller whose implementation on a computer‐coupled laboratory fermentor was presented earlier is briefly reviewed. The slow rate of approach to QSS of the uncontrolled process is verified experimentally. The ability of the control system to rapidly force the system to QSS is demonstrated by a run in which three different QSS points are achieved in a single 12 hr fermentation. The nonlinear nature of the process and the ability of the control system to handle this is demonstrated by comparing the response times to command inputs of different sizes. Noninteraction between cell and substrate response modes is demonstrated. The ability of the system to manipulate substrate concentration in the vessel without a direct measure of it is

ISSN:0006-3592    

DOI:10.1002/bit.260230503

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe theoretical dynamic characteristics of an isothermal continuous flow stirred tank enzyme reactor (CFSTER) operating on two substrates are investigated. Under certain conditions multiple steady states are possible; namely, with an enzyme which binds with the two substrates sequentially. The occurrence of multiple steady states is found to be primarily dictated by three dimensionless parameters which incorporate rate law constants. The global stability of certain steady states is examined by numerically solving the transient material balance on the CFSTER. The effect of recycle on the dynamics of an isothermal plug flow enzyme reactor (PFER) is also studied. A general conclusion indicated by this work is that any open isothermal reaction system wherein the reaction rate law passes through a maximum with increasing substrate concentration and where back mixing occurs with exhibit multiple steady‐state behavior in some operating rang

ISSN:0006-3592    

DOI:10.1002/bit.260230504

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe homogeneity of a purified ribonuclease from brewers' yeast was determined by velocity sedimentation and polyacrylamide gel electrophoresis techniques. The velocity sedimentation pattern gave a single peak with aSapp3.46 and polyacrylamide gel electrophoresis showed one major band. The absorption spectrum of the enzyme showed maximum absorption at 277–278 nm and minimum at 252 nm. The enzyme was relatively stable to extreme pH values and high temperature. Both NaCl and KCl increased the enzyme activity whereas enzyme was inhibited by divalent metal ions. The inhibition of the enzyme was increased in the order of Ca2+>Mg2+>Fe2+Cu2+. Chemical modification studies of the enzyme showed that tryptophan residues and disulfide bonds were required for enzyme activit

ISSN:0006-3592    

DOI:10.1002/bit.260230505

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

年代:1981

数据来源: WILEY

摘要:

AbstractThis study was carried out to define how the overall rate of reaction would be influenced by different degrees of diffusional resistance to cofactor transport within an oxidoreductase membrane matrix. To accomplish this, 0.7–6.6μMyeast alcohol dehydrogenase was immobilized in an albumin matrix crosslinked with 2.5 or 5.0% glutaraldehyde to give 102–1685 μM thick membranes. The enzyme half‐life was at least doubled at pH 7.5 or 8.8 on immobilization. Values of the kinetic constants for the soluble and immobilized enzyme were determined at 25°C and pH 8.8 over the range of 0.01–1.0Mbulk solution concentration of ethanol as substrate and 140–1000μMbulk solution concentration of nicotinamide adenine dinucleotide (NAD+) as cofactor, to give essentially single substrate kinetics in NAD+. Equilibrium partitioning of ethanol and NAD+between the solution and membrane was measured and used in the data analysis. The four kinetic constants for the soluble enzyme agreed with literature values; and all increased with immobilization of the enzyme. The Michaelis constants for NAD+and for ethanol were greater for the immobilized enzyme. The diffusional resistance to NAD+transport, presented in terms of the Thiele modulus, showed that the overall rate of reaction was decreased by about 50% even at values of the modulus

ISSN:0006-3592    

DOI:10.1002/bit.260230506

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

年代:1981

数据来源: WILEY

摘要:

AbstractMicrocarrier cell culture technology has been extended by the finding that two mammalian epithelial cell lines can be continuously subcultured by simple bead‐to‐bead transfer in normal medium in which calcium concentrations have been reduced. Data are reported which show that the hamster ovary line CHO‐Kl and the monkey kidney line LLC‐MK2can be subcultured simply by adding fresh microcarriers to the stirred suspension culture. Thirteen generations of continuous exponential growth are demonstrated with two such subcultures for the CHO‐Kl cells and with four such subcultures for the LLC‐MK2cells. Cell generation times were unchanged by this subculturing approach compared to standard subculturing procedure using trypsin to remove cells from surfaces. We have applied this technique to the production of vesicular stomatitis virus (VSV) from CHO‐Kl cells. Viral yields were comparable (less than twofold difference) in microcarrier cultures which were subcultured via bead‐to‐bead transfer or by the standard means of removing cells from microcarr

ISSN:0006-3592    

DOI:10.1002/bit.260230507

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

年代:1981

数据来源: WILEY

摘要:

AbstractThree freshwater and one marine algal species were grown under inorganic carbon limitation in laboratory continuous cultures. Comparisons were made between HCO3−alkalinity and bubbled CO2as carbon sources. HCO3−alkalinity was an excellent source of inorganic carbon below specific pH levels, but chemical precipitation at high pH placed an upper limit on productivity that was far lower than potential light‐limiting levels. With bubbled CO2it was possible to achieve light limitation. The main factor controlling productivity was the mass flux of inorganic carbon added to the culture, which is the product of gas flow rate and influentP CO 2level. Small bubbles were more efficient than large bubbles at low gas flow rates andP CO 2levels, but led to froth flotation of algal cells and concomitant reductions in productivity at high bubble rates. At 1% CO2productivity was still dependent on mass fluxes of added carbon, but was independent of bubble size. At high bubble rates with 1% CO2narcosis was evident. Maximum yields occurred at intermediate dilution rates when inorganic carbon was supplied vi

ISSN:0006-3592    

DOI:10.1002/bit.260230508

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe growth ofE. coliW in a bench scale fermentor to high cell concentration is described. The method involves growth‐linked introduction of ammonia to the culture, sparging the culture with oxygen, and maintenance of aerobic conditions during the final growth phase by gradually and automatically decreasing the concentration of the carbon source, sucrose, in the culture. Thus, the oxygen demand is kept within the limits of the supply capacity, and a linear growth rate during the final phase of growth is obtained. A concentration of 42 g dry cell per liter was obtained. The yield constants for nitrogen and phosphorous were determined and were compared with those obtained using the temperature variation metho

ISSN:0006-3592    

DOI:10.1002/bit.260230509

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

年代:1981

数据来源: WILEY

摘要:

AbstractSaccharomyces cerevisiaeCBS 426 was grown aerobically and anaerobically in a glucose‐limited chemostat. The flows of biomass, glucose, ethanol, carbon dioxide, oxygen, glycerol, and the elemental composition of the biomass were measured. Models for anaerobic and aerobic growth are constructed. Values forYATPand P/O are obtained from continuous culture data for aerobic growth; thisYATPvalue is compared with that obtained from the anaerobic growth results. The ratio between the heat produced and the oxygen consumed increases if more glucose in fermented to ethanol and carbon dioxide. An equation for ϕH/ϕOas a function of the respiratory quotient is gi

ISSN:0006-3592    

DOI:10.1002/bit.260230510

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

年代:1981

数据来源: WILEY

摘要:

AbstractRates of oxygen absorption into glucose solutions were measured using an immobilized‐enzyme reactor, in which magnetite‐containing beads of immobilized glucose oxidase were moved by a revolving magnetic field to reduce the mass transfer resistances at the gas–liquid interface and around the bead. Data were also obtained for oxygen absorption into glucose solutions containing soluble or immobilized glucose oxidase (without magnetite), as well as for physical absorption of oxygen. The rates of physical absorption for the runs with the magnetite‐containing beads increased because of mechanical stirring caused by spinning of the beads at the gas‐liquid interface. In this case the experimental enhancement factors were found to be larger than those predicted on the basis of the film theory for gas absorption with a pseudo‐first ord

ISSN:0006-3592    

DOI:10.1002/bit.260230511

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

年代:1981

数据来源: WILEY

摘要:

AbstractYeast–lytic enzymes have been isolated on a pilot scale fromCytophagaspecies by precipitation and the light, enzyme‐rich solid phase recovered by liquid‐liquid separation. The enzyme complex was immobilized to soluble polymeric carbohydrates and the effectiveness of the free and immobilized enzyme for protein release and cell debris dissolution has been ass

ISSN:0006-3592    

DOI:10.1002/bit.260230512

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

年代:1981

数据来源: WILEY