摘要:

AbstractConventional experimental design techniques are available to assist in the optimization of fermentation processes, but due to the nonlinearities in the bioprocess, they are limited in their effectiveness. This problem is further complicated with recombinant systems as a result of the additional complexities of the process. This article describes a general strategy using artificial neural networks as an alternative approach to fermentation process development laboratory are presented for the neural network based procedures. © 1994 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260440402

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

年代:1994

数据来源: WILEY

摘要:

AbstractA number of novel redox surfactants (based on mixed bipyridine/dipyridylamine complexes of osmium (II) where the dipyridylamine ligands bears a saturated C8, C10, C12, C14, or C16alkyl chain) were synthesized and characterized electrochemically and biochemically as mediators for glucose oxidase (EC 1.1.3.4, GOD) ofAspergillus niger.These compounds exhibited critical micelle concentrations (CMCs) in phosphate‐buffered saline solution (pH 7.4) in the range 10−410 10−3M, the value decreasing with increasing chain length. Dependence of a number of properties (speed of mediation, redox potential, denaturing action on the enzyme, adsorption on an electrode surface) on the length of the mediator alkyl chain was observed. The presence of an alkyl chain decreased the rate of mediation relative to otherwise similar nonsurfactant mediators, and the longer alkyl chain, the slower the rate of mediation. For each compound, mediation above the CMC was about tenfold slower than that observed below the CMC. However, for the cases of mediator absorbed on an electrode surface with GOD, longer chains give increased physisorption of mixed micelles of enzyme and mediator. The compounds were incidentally found to inhibit the glucose oxidase activity of GOD in a complex manner; inhibition increased with increasing chain length and the deactivation, for any given compound, was more pronounced below the CMC than above. Glucose oxidase activity assays and study of the action of surfactants and mediators on the fluorescent properties of carboxy‐fluorescein‐labeled GOD led to the consideration of a model for redox surfactant‐GOD interaction where three mechanisms may operate: first, a selective interaction of mediators with the GOD active site; second, a nondenaturing association of short‐chain (

ISSN:0006-3592    

DOI:10.1002/bit.260440403

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn experimental method for studying microaerobic fermentation, called oxygen programmed fermentation, is introduced. The method if based on a chemostat. The mathematical equations governing the dynamics of the system are derived and simulations are made for two principally different cases: a purely respirative organism, and an organism capable of fermentation during oxygen limitation. It is shown that at a suitably chosen ramp rate, the dissolved oxygen concentration in the broth can be made to decrease almost linearly. It is suggested that the greatest use of oxygen programmed fermentation will be in initial experiments. Compared with chemostat studies, a scan of different oxygenation rates will provide a time‐saving method of finding the interacting regions for metabolic transitions. Furthermore it is shown that the methods makes it possible to study cell physiology at condition which would normally lead to washout. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260440404

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

年代:1994

数据来源: WILEY

摘要:

AbstractA new experimental technique, called oxygen programmed fermentation (OPF), was used to study microbial cultures of the yearsPichia stipitisandCandida utilisgrowing on xylose as carbon and energy source. In the oxygen programmed fermentation, the inlet oxygen mole fraction was continuously changed to scan through a wide range of oxygen uptake rates in a continuous culture. The largest ethanol yields and productivities ofP. stipitiswere found at oxygen transfer rates below 1.5 mmol L−1h−1. It was found that the ratio between the culture fluorescence and near‐IR absorbance increased at oxygen transfer rates lower than 1.5 mmol L−1h−1. Small amounts of ethanol were produced also byC. utiliswhen the oxygen transfer rate was between 0 and 3 mmol L−1h−1. It is suggested that OPF will form a nice complement to ordinary, microaerobic chemostat experiments, by making the identification of interesting regions of oxygen transfer rates possible in an efficient and time‐saving initial experiment. © 1994 John

ISSN:0006-3592    

DOI:10.1002/bit.260440405

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

年代:1994

数据来源: WILEY

摘要:

AbstractBatch and continuous hydrolysis of olive oil in an organic‐aqueous two‐phase system using the live whole cell ofPseudomonas putida3SK as a source of a lipase is investigated. The strain was not only fully viable and grown well, but also produced extracellular lipase simultaneously. The degree of hydrolysis, depending on olive oil concentration in the solvents, was maximal at 13.5% (w/v) and decreased with the increase of the substrate concentration. At the optimal condition, a degree of hydrolysis higher than 95% was achieved with 24 h at 30°C when the reaction was carried out in a two‐phase batch stirred reactor. For long‐term operation a continuous stirred reactor was designed. When the reaction was carried out in a continuous stirred reactor, the degree was hydrolysis reached 86% at a dilution rate of 0.2 h−1. Satisfactory performance of a two‐phase bioreactor was obtained in a long‐term continous operation, which lasted for at least 30 days by feeding organic solvent containing olive oil and aqueous media separately. © 1994 John

ISSN:0006-3592    

DOI:10.1002/bit.260440406

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe partitioning of pristinamycins was studied in dextran and polyethylene glycol (PEG) aqueous two‐phases systems. Pristinamycins partitioned preferentially into the PEG‐rich top phase. The partition coefficient was independent of molar mass of PEG and dextran and of antibiotic concentration, but, increased exponentially with the tieline length of the system. Partition of pristinamycins was greatly improved when fatty acids esters of PEG were mixed with PEG. In such mixtures, the partition of coefficient increased up to a value of 24, dependent on the carbon chain length of fatty acids and the modified PEG concentrations. Moreover, in such system, the two groups of pristinamycins, I and II, were extracted in accordance with their hydrophobicity. Recovery of pristinanamycins produced byStreptomyces pritinaespiralisin a fermentation broth was achieved with a dextran/PEG system. Cells were confined into the bottom phase and pristinamycins partitioned in the top phase. However, due to binding of the pristinamycins to the cells, the partition coefficient was slightly lower than of pure antibiotics solutions. © 1994 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260440407

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe amino acid fermentation byCorynebacterium glutamicumwas monitored with an new technique that uses the first derivative of the NAD(P)H fluorescene signal. The rate of change of NAD(P)H pools is indicative of intracellular redox balance variations that correspond to metabolic changes. The profile of this signal showed several characteristics that coincided with major metabolic events during fermentation. We show here that the derivative fluorescence signal can accurately estimate points of threonine depletion, viable cell count, and the end of amino acid formation. Furthermore, on‐line optimization strategies can be developed by using the derivative fluorescene signal. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260440408

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

年代:1994

数据来源: WILEY

摘要:

AbstractOxygen and nutrient limitation was investigated in order to identify the origin of a lower specific ajmalicine production inCatharanthus roseuscultures at high cell densities in an induction medium. The effect of oxygen limitation was explored by comparing two identically aerated and agitated high cell density bioreactor cultures with dissolved oxygen (DO) concentration of 15% and 85% of air saturation, with respect to alkaloid formation and related enzymes activities. Oxygen had an evident effect on ajmalicine production: in the high DO cultures production was more than 5 times higher than in the low DO cultures. The difference in ajmalicine production between high and low DO could not be explained by the enzyme activity profiles. Moreover, the productivity in the high density culture could not restored to the level of a low density culture (at a high DO) by increasing the DO alone. The effect of nutrient limitation was studied with response surface methodology in shake flask cultures. Nutrient limitation could not be demonstrated to be responsible for the productivity loss. Alkaloid and enzyme measurements in the shake flask cultures supported previous findings that the tryptamine pathway may regulate alkaloid production, provided that the terpenoid pathway is sufficiently active. © 1994 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260440409

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe application of the expanded granular sludge bed (EGSB) reactor for the anaerobic treatment of low‐strength soluble wastewaters using ethanol as a model substrate was investigated in laboratory‐scale reactors at 30oC. Chemical oxygen demand (COD) removal efficiency was above 80% at organic loading rates up to12 g COD/L · d with influent concentrations as low as 100 to 200 mg COD/L. These results demonstrate the suitability of the EGBS reactor for the anaerobic treatment of low‐strength wastewaters. The high treatment performance can be attributed to the intense mixing regime obtained by high hydraulic and organic loads. Good mixing of the bulk liquid phase for the substrate‐biomass contact and adequate expansion of the substrate‐biomass contact and adequate expansion of the sludge bed for the degassing were obtained when the liquid upflow velocity (Vup) was greater than 2.5 m/h. Under such conditions, an extremely low apparentKsvalue for acetoclastic methanogenesis of 9.8 mg COD/L was observed. The presence of dissolved oxygen in the wastewater had no detrimental effect on the treatment performance. Sludge piston flotation from pockets of biogas accumulating under the sludge bed occurred atVuplower than 2.5 m/h due to poor bed expansion. This problem is expected only in small diameter laboratory‐scale reactors. A. more important restriction of the EGSB reactor was the sludge washout occurring atVuphigher than 5.5 m/h and which was intensified at organic loads higher than 7 g COD/L· d due to buoyancy forces from the gas production. To achieve an equilibrium between the mixing intensity and the sludge hold‐up, the operation should be limited to an organic loading rate of 7 g COD/L d· and to a liquid up‐flow velocity between 2.5 and 5.5 m/h © 1994 J

ISSN:0006-3592    

DOI:10.1002/bit.260440410

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

年代:1994

数据来源: WILEY

摘要:

AbstractFoam development and stability inAtropa belladonnasuspensions were investigated as a function of culture conditions. Foaming was due mainly to properties of the cell‐free broth and was correlated with protein content; effects due to presence of cells increased towards the end of batch culture. Highest foam levels were measured 11 days after inoculation. Air flow rate was of major importance in determining foam volume; foam volume and stability were also strongly dependent on pH. Foam flotation of plant cells was very effective. After 30 min foaming, ca. 55% of cells were found in the foam; this increased to ca. 75% after 90 min. Polypropylene glycol 1025 and 2025, Pluronic PE 6100, and Antifoam‐C emulsion were tested as chemical antifoams. Polypropylene glycol 1025 and Antifoam C at concentrations up to 600 ppm had no adverse effect on growth in shake flasks; Pluronic PE 6100 has an inhibitory effect at all levels tested. Concentrations of polypropylene glycol 2025 and Pluronic PE 6100 as low as 20 ppm reduced foam volumes by a factor of ca. 10. Addition of antifoam reducedkLavalues in bubble‐column and stirred‐tank bioreactors. After operation of a stirred reactor for 2 days using Antifoam C for foam control, cell production was limited by oxygen due to the effect of antifoam on mass transfer. Theoretical analysis showed that maximum cell concentrations and biomass levels decline with increasing reactors working volume due to greater consumption of antifoam to prevent foam overflow. The results indicate that when chemical foam control is used in plant cell cultures, head‐space volume and tolerable foam levels must be considered to optimize biomass production. © 1994 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260440411

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

年代:1994

数据来源: WILEY