摘要:

AbstractThe enzymatic hydrolysis of olive oil usingChromobacterium viscosumlipase B encapsulated in reversed micelles of dioctyl sodium sulfosuccinate (AOT) in isooctane was investigated in an ultrafiltration ceramic membrane reactor of tubular type, operating in a batch mode. Water concentration was found to be a critical parameter in the enzyme kinetics and hydrolysis yield of the reaction. The size of micelles, recirculation rate, and substrate concentration were found to be the major factors affecting the separation process. A correlation that enables the prediction of final conversion degrees in this bioreactor from the initial reaction conditions was established. © 1993 Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410802

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe growth of plant cell suspension cultures ofCatharanthus roseusin batch fermentors was studied at different initial phosphate levels of the medium. On the basis of the observations and existing knowledge with respect to phosphate metabolism in culturedC. roseuscells, a structured mathematical model was developed for the description of the kinetics of growth and intracellular accumulation of glucose and phosphate, as a function of glucose and phosphate supply. It was shown that the model offers not only good description of the growth of the cells in batch culture at different initial phosphate levels, but also provided a satisfactory description of the growth in glucose limited chemostats. © 1993 Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410803

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

年代:1993

数据来源: WILEY

摘要:

AbstractFed‐batch techniques were employed to obtain high cell density cultures (92–100 g DCW/L) ofEscherichia colistrain X90 producing a recombinant serine protease, rat anionic trypsin, secreted to the periplasm. The specific growth rate was controlled to minimize growth‐inhibiting acetate formation by utilizing an exponential feeding profile determined from mass balance equation. The volumetric yield of recombinant rat anionic trypsin was 56 mg/L, and the final cell density was 92 g DCW/L when the culture was induced in the late logarithmic phase. However, when the culture was induced in the early logarithmic phase, the volumetric yield was 13 mg/L and the final cell density was 14 g DCW/L. Thus, the induction timing is shown to have a significant effect on the final cell density as well as the overall volumetric yield of the recombinant protease. © 1993 Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260410804

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe potential for producing acetoin and butanediol with aBacillus subtilisstrain was investigated with continuous culture using molasses as carbon substrate. The steady‐state results were influenced by both oxygen and undetermined limiting compounds. Employing the known metabolic pathways, four overall stoichiometry relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relation between the overall rates, whose parameters were determined by linear regression. This provided a relationship for the product formation rate. The chemostat culture data were described with a growth kinetics model, which included limitation by molasses and oxygen as well as diauxic effects and product inhibition. The biokinetics model was combined with an experimentally verified model for the membrane Pervaporation. From this combined model were determined the influence of the membrane characteristics (enrichment factors and membrane area) and the dilution rate on the performance of the integrated process. Simulations revealed that an increase of the enrichment factor, possible by membrane improvement, would have counteracting influences, owing to decreased product inhibition but with lower biomass concentration. © 1993 Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260410805

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

年代:1993

数据来源: WILEY

摘要:

AbstractSaccharomyces cerevisiaeautoselection strains with mutations in theura3, fur1, andurid‐kgenes have been obtained through a sequential isolation procedure. This autoselection system is an extension of one described by Loison et al. The mutations effectively block both the pyrimidine biosynthetic and salvage pathways and in combination are lethal to the host. Therefore, a plasmidencodedURA3gene is essential for cell viability regardless of the growth conditions, and complex (traditionally nonselective) media can be employed without the risk of plasmid loss. The effects of medium enrichment on growth and cloned gene product synthesis were examined in batch culture for two autoselection strains. The plasmid gene product β‐galactosidase was under the control of the yeastGAL1promoter, and two methods of induction were employed; one strain was induced via temperature shift while the other was induced by galactose addition. Three nutrient media were investigated: a lean selective medium (SD), a richer semidefined medium (SDC), and a rich complex medium (YPD). The results demonstrated the improvements in cloned gene productivity possible when the growth medium is enriched, with up to 10‐fold increases in β‐galactosidase productivity observed. Plasmid instability and mutation reversion were not problems for the autoselection strains, even in uracil‐containing medium. Short‐term plasmid stabilities were approximately 90% in all three media tested. During continuous culture of the autoselection temperature‐sensitive strain, long‐term plasmid stability was excellent and β‐galactosidase expression remained high after more than 25 residence times under inducing conditions. In contrast, both β‐galactosidase specific activity and plasmid stability decreased linearly with time for an analogous nonautoselection strain. The introducedfur1anduridkmutations were very stable; after more than 50 generations of growth in complex medium, stability values of 99–100% were measure

ISSN:0006-3592    

DOI:10.1002/bit.260410806

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe population dynamics of developing somatic embryos of carrot (Daucur carota L.) was investigated in batch and fed‐batch cultures using modified Murashige and Skoog medium. These substrate limitations coincided not only with stoppage of biomass increase, but also with the increase in total concentration of embryos as well as the advancement of the embryo into a more mature stage. Both glucose and ammonium were depleted from the culture. Restoring either glucose, or ammonium and nitrate, as to approximately initial concentrations in fed‐batch experiments, did not result in a significant increase of the total normal embryo concentration. On the other hand, medium replacement led to increase in biomass concentration, total embryo number, and improved embryo maturity. The addition of a mixture of glucose, ammonium, and nitrate to the spent medium resulted in variable increases in biomass and embryo number, but always less than those resulting from media replacement. Although the total number of embryos was higher after medium replacement, the fraction of embryos reaching torpedo stage was still only 50%. The need for a better means of population characterization for further kinetic studies is discussed. © 1993 Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410807

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

年代:1993

数据来源: WILEY

摘要:

AbstractBiomass of nonliving, dried brown marine algaeSargassum natans, Fucus vesiculosus, andAscophyllum nodosumdemonstrated high equilibrium uptake of cadmium from aqueous solutions. The metal uptake of cadmium from aqueous solutions. The metal uptake by these materials was quantitatively evaluated using sorption isotherms. Biomass ofA. nodosumaccumulated the highest amount of cadmium exceeding 100 mg Cd2+/g (at the residual concentration of 100 mg Cd/L and pH 3.5), outperforming a commercial ion exchange resin DUOLITE GT–73. A new biosorbent material based onA. nodosumbiomass was obtained by reinforcing the algal biomass by formaldehyde cross–linking. The prepared sorbent possessed good mechanical properties, chemical stability of the cell wall polysaccharides and low swelling volume. Desorption of deposited cadmium with 0.1−0.5M HCI resulted in no changes of the biosorbent metal uptake capacity through five subsequent adsorption/desorption cycles. There was no damage to the biosorbent which retained its macroscopic appearance and performance in repeated metal uptake/elution cycles. © 1993 Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260410808

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

年代:1993

数据来源: WILEY

摘要:

AbstractCadmium uptake by nonliving and resting cells ofSaccharomyces cerevisiaeobtained from aerobic or anaerobic cultures from pure cadmium‐bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal‐sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. © 1993 Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410809

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn algorithm developed for pH computation has been tested to calculate the theoretical pH changes in a culture medium during the course of a fermentation. A divergence between the computed pH value and the value measured with the electrode allows us to highlight the presence of undetected ionic products. The calculation with the algorithm by means of a computer requires only the knowledge of the ionic properties of the substrates and detected products and existing thermodynamic constants. © 1993 Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410810

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

年代:1993

数据来源: WILEY

摘要:

AbstractImmobilization of phospholipase D from cabbage was studied with the aim of stabilizing the enzyme for its use in synthesis of phospholipids. It was shown that phospholipase D can be immobilized by adsorption to polymeric carriers containing long chain anchor groups such as octadecyl, octyl, or other alkyl residues. Starting from the crude enzyme, phospholipase D activity is preferentially bound (up to 100%) in competition with contaminating proteins. A prerequisite of high binding rates is the presence of calcium ions, which play a mediating role in the adsorption process. The maximum activity of the carrier‐enzyme complexes depends upon the calcium concentration in the immobilization process and the carrier material (≥10mMCaCl2with octadecyl‐Si40, ≥40 mMCaCl2with octyl‐sepharose and butyl‐fractogel). Immobilization of phospholipase D to octyl‐sepharose was shown to result in a distinctly increased storage stability and an enlarged pH‐optimum range for the catalytic activity. Operational stability of different phospholipase D‐carrier complexes was compared. © 19

ISSN:0006-3592    

DOI:10.1002/bit.260410811

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

年代:1993

数据来源: WILEY