摘要:

AbstractThe method of using liquid emulsion membranes featuring the cation carrier D2EHPA [di‐(2‐ethylhexyl) phosphoric acid] for the separation ofL‐phenylalanine is examined. Results from experiments performed under various conditions are discussed and an optimal condition for separation is determined. The selectivity of the liquid emulsion membrane system is discussed. The effects of impurities such as sodium chloride, glucose, lactic acid, andL‐tryptophan on the transport ofL‐phenylalanine are evaluated. It is shown that the liquid emulsion membrane system is a potential operation not only to separateL‐phenylalanine but also concentrate it with great

ISSN:0006-3592    

DOI:10.1002/bit.260350902

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn extractive acetonobutylic fermentation process is developed by integrating bioproduction, Ultrafiltration, and distillation, providing simultaneous retention of biomass, selective removal of inhibitors from the permeate, as well as separation and purification of acetone–butanol–ethanol solvents. Successive batch fermentations were performed with normal pressure distillation (98°C), which permitted prolonging and enhancing (by a factor of 3) solvent production, with very few volume exchanges of medium (average dilution rate ws 0.002 h−1), and recovering on‐line concentrated solvents. Different operating conditions were also tested in order to study the presence of extracellular autolytic enzymes as inhibition factors: It was shown that, (1) extracellular autolytic activity remains low during the larger part of fermentations, even without enzyme‐inactivating thermotreatment in the distillation boiler, and (2) high‐temperature distillation causes deleterious effects to the culture medium for long duration treatments. Progressive improvements of the process were achieved, first, by managing continuous runs, providing a minimum renewal of the culture medium and, mainly, by decreasing temperature and pressure of distilation. Solvent productivity then reached 2.6 g/L h for a 0.036 h−1average dilution rate, corresponding to a feed concentration of 156 g/L glucose act

ISSN:0006-3592    

DOI:10.1002/bit.260350903

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

年代:1990

数据来源: WILEY

摘要:

AbstractCharacterization of mycelial morphology is important for physiological and engineering studies of filamentous fermentations, and in the design and operation of such fermentations. Image analysis has been developed as a method for this characterization, and has been shown to be faster and generally more accurate than previous methods. A fully automatic system has been developed, in which speed is gained, but with loss of accuracy in some cases. The method has been tested onStreptomyces clavuligerusandPenicillium chrysogenumP1 batch fermentations. It has also been tested on a fed‐batchPenicillium chrysogenumP2 fermentation, in which the medium contained solid ingredients. Fully automatic image analysis for morphological characterization of filamentous microorganisms is an important development which will make practical many engineering and physiological studies of such fermentations that have so far not been completely satisfactor

ISSN:0006-3592    

DOI:10.1002/bit.260350904

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

年代:1990

数据来源: WILEY

摘要:

AbstractA mouse–mouse hybridoma was grown in serum‐free medium supplemented with bovine milk or colostrum. Bovine colostrum supported growth of the hybridoma whereas bovine milk alone did not support cellular proliferation. For growth in medium supplemented with colostrum, the maximum cell concentration achieved was 1.4 × 106cells/mL in 2.2% colostrum, which is 44% of that obtained in 9% serum. When cells were grown in media containing milk and low amounts of serum (<1%) the maximum cell concentration in 2.2% milk with 0.4% serum was 2 × 106cells/ml, whereas it was only 0.2 × 106cells/ml and 1.3 × 106cells/ml in 2.2% milk alone and 0.4% serum alone, respectively. Similar behavior was observed for growth in media containing colostrum and low amounts of serum. The monoclonal antibody production in media containing combinations of serum and milk or colostrum was comparable to that obtained in media with higher serum concentrations. Experiments performed with conditioned media suggest that the rapid decrease in viability, after the maximum cell concentration has been reached, is partially due to the presence of some inhibitory components generated during the cell culture rather than due to depletion of some serum com

ISSN:0006-3592    

DOI:10.1002/bit.260350905

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn submerged cultures,Streptomyces tendaetended to form fluffy spherical pellets of the noncoagulative type. An increase in the average pellet size could be attained by decreasing any of the following: shear rate, pH, temperature, or inoculum size. Conditions leading to oxygen limitation tended to reduce the average pellet size and induced pulpy growth, whereas oxygen sufficiency seemed to induce pellet formation. Factors inducing pellet formation simultaneously increased cell wall hydrophobicity. It is therefore proposed that the main forces inducing cellular aggregation inS. tendaeare hydrophobic interactions of cell walls, and these interactions are controlled by availability of dissolved oxygen.

ISSN:0006-3592    

DOI:10.1002/bit.260350906

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

年代:1990

数据来源: WILEY

摘要:

AbstractA mathematical model for the effects of NH4Cl addition to the growth medium on hybridoma cell intracellular pH (pHi) is presented which includes a detailed description of the properties of the Na+/H+exchanger. The model is used to calculate the steady‐state value of pHias a function of the extracellular NH4Cl concentration, employing parameter values taken from the literature except for the cell permeability to NH4+This parameter value, estimated to be 3.5 × 10−7cm/s, is obtained by fitting simulation results to experimental data obtained previously for the steady‐state value of pHiin the presence of 10mMNH4Cl. The model simulates well the major features of previously observed experimental pHichanges following NH4Cl addition: the transient characteristics, dependence on the NH4Cl concentration, and lack of dependence on the external pH value. The effect of parameter variations on model results is also investigated in additional simulations. The general modeling framework employed here should be useful for other types of mammalian

ISSN:0006-3592    

DOI:10.1002/bit.260350907

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

年代:1990

数据来源: WILEY

摘要:

AbstractA general model for aerobic yeast growth in batch culture is presented. It is based on the concept that the aerobic metabolism of all yeasts is determined by the relative sizes of the transport rate of sugar into the cell and the transport rate of respiratory intermediates into the mitochondrion. If the rate of sugar uptake rate exceeds the rate of transport of respiratory intermediates into the mitochondrion (as inSaccharomyces cerevisiae, S. uvarum, andS. pombe), the metabolism exhibits the features of ethanol excretion and limited specific oxygen uptake rate. If the rate of transport of respiratory intermediates into the mitochondrion is of the same order as the transport of sugar into the cell (as inCandida utilis), the metabolism is characterized by little or no ethanol excretion and a much higher specific oxygen uptake rate. Batch data from an extensive range of yeast and carbon sources is used to illustrate the use of this model. The ability of this model to fit such an extensive range of experimental data suggests that it can be used as a generalized model for aerobic yeast growth.

ISSN:0006-3592    

DOI:10.1002/bit.260350908

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

年代:1990

数据来源: WILEY

摘要:

AbstractA general model for the aerobic growth of yeast in continuous culture is presented. The model is capable of simulating the complete range of metabolic responses observed for yeast growth in continuous culture including respiratory repression, saturated respiratory capacity, and respiratory depression.It is postulated that respiratory depression is the result of the adaptation (increase in capacity of the respiratory intermediate transport proteins located at the mitochondrial membrane). Respiratory repression and subsequent saturated respiratory capacity is postulated to be the result of the gradual transfer of biosynthetic intermediates provision from the mitochondrion to the cytoplasm or, possibly, the adaptation (increase) in the capacity of the cell to excrete ethnol. It is difficult to provide a definitive experimental verification of these postulates.Irrespective of the biochemical basis of respiratory repression and depression, the model described is capable of simulating the complete range of metabolic responses obtained for yeast growth in continuous culture. It is the only model reported in the literature capable of achieving this.

ISSN:0006-3592    

DOI:10.1002/bit.260350909

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe stereoselective reduction of ethyl acetoacetate to (+)‐(S)‐ethyl 3‐hydroxybutyrate catalyzed bySaccharomyces cerevisiaewas optimized by means of chemometric methods. The quantitative effects of temperature, time of incubation, and concentrations of yeast and substrate on the optical purity and on the percent of reduced substrate were investigated using a factorial design at two levels. This approach gave information about the chemical behavior of the catalyst. The variability of the two responses was expressed by means of their corresponding response surfaces. Use of desirability functions allowed the overall optimization of the process, also taking into account the importance of economic factors. The investigation showed that it is possible to reduce the substrate completely obtaining (+)‐(S)‐ethyl 3‐hydroxybutyrate with percent of enantiomeric excess>98% and, at the same time, to operate in more convenient experimental conditions than those previous

ISSN:0006-3592    

DOI:10.1002/bit.260350910

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

年代:1990

数据来源: WILEY

摘要:

AbstractElectrochemical regeneration of NAD was performed at a laboratory preparative scale to illustrate both the efficiency and intrinsic simplicity of the electrochemical method. A powerful plug‐flow reactor was realized with a flow through graphite felt electrode, the ratio of the effective area of electrode/volume of reactor increased to 380 cm2/cm3. This graphite‐felt electrode was able to oxidize NADH coenzyme at a very low overvoltage. On the example of the gluconic acid production catalyzed by glucose dehydrogenase, current as high as 0.1 A was obtained in experience where enzymatic activity was the main limitation. In confirmation of our previous work, the results show that the yield of NADH electrochemical oxidation is better than 99.

ISSN:0006-3592    

DOI:10.1002/bit.260350911

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

年代:1990

数据来源: WILEY