摘要:

AbstractA process for the continuous fermentation of the genetically modified, nitrogenase‐producingEscherichia coliC‐M74 (pUS1)‐strain has been developed. This strain, which is able to fix molecular nitrogen, has thenifgenes of the bacteriumKlebsiella pneumoniae. Cell growth and nitrogenase activity of the enzyme have been optimized both in batch and continuous fermentations. For the fermentations, trial runs were performed by cultivating theE. colicells in 50‐ml culture bottles. The medium composition was varied in order to provide high biomass production and nitrogenase activity. For an effective fermentation control, an on‐line analysis was built up for the substrates ammonium and glucose. Other medium components such as ampicillin, citric acid, acetic acid, nitrogenase activity, and protein were measured by using different off‐line methods. Modern optical methods like in‐line microfluorometry for monitoring the culture fluorescence and laser flow cytometry for the estimation of DNA and protein content were also employed. Plasmid stability was al

ISSN:0006-3592    

DOI:10.1002/bit.260381002

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

年代:1991

数据来源: WILEY

摘要:

AbstractMethodology is presented for the determination of growth yield (Yg) and maintenance coefficient (m) for carbon utilization of plant cells grown in suspension culture. Estimation ofYgandmrequires measurements of specific growth rate (µ) and specific rate of substrate uptake (q) at different growth limiting substrate concentrations. Batch culture of tobacco cells did not permit evaluation ofYgandmbecause µ is constant and maximal during most of the growth cycle. In batch culture, the period of declining specific growth rate is extremely brief because of the rapid transition from logarithmic growth to stationary phase. This occurs because theKmfor growth is relatively small compared to the initial sucrose concentration. Thus, when the substrate level reaches theKm, the large mass of cells rapidly depletes the remaining substrate. In contrast, semicontinuous culture facilitates the determination ofYgandmbecause various steady‐state growth rates can be achieved. Mathematical expressions were developed to determine the effective values of µ andqover the semicontinuous replacement interval. The validity of this approach was verified by conducting simulations using experimentally determined parame

ISSN:0006-3592    

DOI:10.1002/bit.260381003

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

年代:1991

数据来源: WILEY

摘要:

AbstractPorcine pancreatic lipase immobilized on celite particles has been employed as a catalyst for the esterification of dodecanol and decanoic acid in a predominantly organic system. Solvent influence on the equilibrium position and on the catalyst activity has been studied using 20 solvents, including aliphatic and aromatic hydrocarbons, ethers, ketones, nitro‐ and halogenated hydrocarbons, and esters. The equilibrium constant for esterification correlates well with the solubility of water in the organic solvent, which in turn shows a good relationship with a function of Guttman's donor number and the electron pair acceptance index number of the solvent. This may be rationalized in terms of the requirements for solvation of water and of the reactants. The catalyst activity, measured as the initial rate of the esterification reaction, is best correlated as a function of bothn‐octanol‐water partition coefficient (logP) and either the electron pair acceptance index or the polarizab

ISSN:0006-3592    

DOI:10.1002/bit.260381004

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe have developed a strategy for immobilization‐stabilization of α‐chymotrypsin by multipoint covalent attachment of the enzyme, through its amino groups, to agarosealdehyde gels. We have studied the role of the main variables that control the intensity of these enzyme‐support multi‐interaction processes (surface density of aldehyde groups in the activated gel, contact time between the immobilized enzyme and the activated support prior to borohydride reduction of the derivatives, etc.). In this way, we have prepared a number of very different chymotrypsinagarose derivatives. Our best derivatives, with the most intense multipoint attachment, were more stable than one‐point attached derivatives and were more than 60,000‐fold more stable than soluble enzyme in the absence of autolysis phenomena. In spite of the dramatic stabilization, the catalytic activity of these derivatives is little changed (they only lose 35% of intrinsic activity after this intense enzyme‐support multi‐interaction process). In addition, we have also demonstrated the very high capacity of 6% aldehyde‐agarose gels to immobilize pure chymotrypsin (40 mg enzyme/mL catalyst). Furthermore, we have been able to establish a clear correlation between enzyme‐support multipoint covalent attachment, stabilization against very different denaturing agents (heat, urea, organic cosolvents), and insensitivity of those immobilized chymotrypsin molecules to so

ISSN:0006-3592    

DOI:10.1002/bit.260381005

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

年代:1991

数据来源: WILEY

摘要:

AbstractAcid phosphatase thermal deactivation follows a complex path: an initial decay toward an equilibrium distribution of at least two intermediate structures, mutually at the equilibrium, followed by a final breakdown toward a completely inactive enzyme configuration. The results obtained in the presence of sorbitol have been compared to those produced in the course of purely thermal deactivation of the native enzyme. For any sobitol concentration, an equivalent temperature is calculated that results in exactly the same activity‐versus‐time profile. This suggests enzyme deactivation to be controlled by a single, unchanging step. Immobilized enzyme runs have been performed, as well, by entrapping acid phosphates within a polymeric network formed onto the upstream surface of an ultrafiltration membrane. The stabilizing effect of entrapment cumulates with that produced by sorbitol. In this case, however, an equivalent temperature cannot be determined, thus indicating that a different deactivation mechanism is follo

ISSN:0006-3592    

DOI:10.1002/bit.260381006

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

年代:1991

数据来源: WILEY

摘要:

AbstractChromobacterium viscosumlipase which has adsorbed on liposome and solubilized in microemulsion droplets of glycerol containing a little amount of water could catalyze the glycerolysis of olive oil. Studies on the continuous glycerolysis of olive oil by the immobilized enzyme was done at 37°C in continuous stirred vessel bioreactor with polysulfone membrane. The effect of the flow rate of substrate (olive oil) in isooctane on the conversion and composition of the outlet was investigated using high‐performance liquid chromatography (HPLC). The conversion increased with decrease in the flow rate. And we studied the effect of water content in the glycerol‐water‐lipase solution on the glycerolysis reaction. The conversion to desirable products, mono‐ and di‐olein, was improved without a substantial production of oleic acid at lower water concentrations, i.e., below 8.0% (w/v) which corresponds to awovalue of 0.97. At water concentration higher than 8.0% (w/v), the amount of free fatty acid was dramatically increased. Higher operational stability of the enzyme reactor, and the half‐line of the enzyme continuous reaction was a

ISSN:0006-3592    

DOI:10.1002/bit.260381007

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

年代:1991

数据来源: WILEY

摘要:

AbstractContinuous production ofL‐alanine with conjugated enzyme systems of alanine dehydrogenase (AlaDH) and lactate dehydrogenase (LDH) or alcohol dehydrogenase (ADH) was carried out with NAD regeneration in an ultrafiltration hollow‐fiber capillary reactor (HFCR) which was proposed as a test bioreactor with very small scale. In the AlaDH/LDH system, pyruvate is the intermediate product forL‐alanine so that an optimal point existed in pyruvate concentration for the production rate ofL‐alanine. NAD cycling number of 4850 andL‐alanine productivity of 61.7 mmol/L h were obtained at the best condition. In the AlaDH/ADH system, however, the substrate inhibition in the AlaDH reaction by pyruvate should be considered and the best results of NAD cycling number andL‐alanine productivity were 2700 and 13.5 mmol/L h, respectively. In consideration of concentration distribution and mixing in the axial direction on an HFCR, performance of the reactor was theoretically analyzed with a multistage stirred tank reactor model combined with the kinetic model based on all the elementary reactions involved. Although quantitative discrepancy existed in some cases, the present theoretical model could explain experimental results and is expected to be generally applicable to standard hollow fib

ISSN:0006-3592    

DOI:10.1002/bit.260381008

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

年代:1991

数据来源: WILEY

摘要:

AbstractBatch and continuous fermentation studies were performed to optimize the production of ammonium lactate from whey to optimize the production of ammonium lactate from whey permeate. The product known as fermented ammoniated condensed whey permeate (FACWP) is a very promising animal feed. After an initial screening of four strains which produce predominantly L(+)‐ lactic acid, the desired isomer [D(−)‐lactic acid is toxic],Streptococcus cremoris2487 was chosen for further study. In batch mode, pH between 6.0 and 6.5 and 35°C provided optimum incubation conditions. To stimulate a plug flow reactor, three CSTRs (continuous stirred tank reactors) were connected in tandem. For a 7.5‐h retention time, 1.6‐fold and 1.3‐fold higher productivities were obtained for three‐stage than for the single‐ and two‐stage reactors, respectively. Various retentions times were examined (5, 7.5, and 10 h; 5g/L yeast extract). Although maximum lactate productivity occurred at a 5‐h residence time (5.38 g/L H. 75% lactose utilization), lactose utilization was more complete at 7.5 h (4.38 g/L h productivity, 91% lactose utilization and a productivity, 91% lactose utilization). Retention time was increased to 15 h to obtain 95.9% lactose utilization and a productivity of 2.42g/L h for 2g/L yeast extract. Based on this lower yeast extract concentration, it was determined that ammonium lactate production and subsequent concentration by 11‐fold would yield a product (FACWP) 17% more than soybean meal (crude protein contents are equivalent, 44%) at

ISSN:0006-3592    

DOI:10.1002/bit.260381009

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

年代:1991

数据来源: WILEY

摘要:

AbstractA photobioreactor system has been designed, constructed and implemented to achieve high photosynthetic rates in high‐density photoautotrophic algal cell suspensions. This unit is designed for efficient oxygen and biomass production rates, and it also can be used for the production of secreted products. A fiber‐optic based optical transmission system that is coupled to an internal light distribution system illuminates the culture volume uniformly, at light intensities of 1.7 mW/cm2over a specific surface area of 3.2 cm2/cm3. Uniform light distribution is achieved throughout the reactor without interfering with the flow pattern required to keep the cells in suspension. An on‐line ultrafiltration unit exchanges spent with fresh medium, and its use results in very high cell densities, up to 109cells/mL [3% (w/v)] for eukaryotic green algachlorella vulgaris. DNA histograms obtained form flow cytometric analysis reveal that on‐line ultrafiltration influences the growth pattern. Prior to ultrafiltration the cells seem to have at a particular point in the cell cycle where they contain multiple chromosomal equivalents. Following ultrafiltration, these cells divide, and the new cells are committed to division so that cell growth resumes. The Prototype photobioreactor system was operated both in batch and in continuous mode for over 2 months. The measured oxygen production rate of 4‐6 mmol/L culture h under continuous operation is consistent with the predicted performance of the unit for the provided light

ISSN:0006-3592    

DOI:10.1002/bit.260381010

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

年代:1991

数据来源: WILEY

摘要:

AbstractA continuous centrifugal bioreactor (CCBR), developed to study the growth and productivity of dense suspensions cultures, has been applied to both fermentation and mammalian cell cultivation processes. With this approach, high‐density nonflocculent cultures are maintained in a tapered fluidized bed by balancing the drag forces on the cells due to following substrate with the centrifugal forces. The Sysyem was first used to produce ethanol by fermentation withSaccharomyces cerevisiae;then with H21A1 mouse hybridoma cells secreting monoclonal antibody (MoAb), lgM. Results of this research show the feasibility of using the CCBR for both production of secreted products and as a research tool for studying cell metabolism and production kinetics. Media recycle may be used to modify the behavior of the system form a plug flow apparatus to a continuous stirred reactor (CSTR

ISSN:0006-3592    

DOI:10.1002/bit.260381011

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

年代:1991

数据来源: WILEY