摘要:

AbstractBacteria rapidly metabolize sugars and produce heat accordingly (Escherichia coli, aerobic conditions, 25°C). Two kinds of heat output are gotten: (1) from excess cells and limiting carbon, 2 × 109to 5 × 109cells, 5‐50 nanomole glucose; (2) from limited cells and excess carbon, 0. 1 × 109‐1 × 109bacteria and 200‐600 nmol glucose. The thermograms from heat conduction calorimetry under the first conditions measure velocities of sugar uptake and initial metabolic throughput in 1‐6‐min time spans before a growth cycle possibly can occur. Under the second conditions with limited cells, power output plateaus to a steady state proportional to cell biomass and number of cells. In order to evaluate the calorimetric means for measuring number of cells, six independent means including spectrophotometry (turbidity) were compared: microkjeldahl nitrogen, biuret protein, dry weight, microscopy direct counting in Petroff‐Hausser chambers, and viable colony counting. Using turbidity as a central standard, all methods including calorimetry under the second set of conditions agree within ±18% of one another. Spectrophotometry is the most rapid method but is seriously interfered with by pigments that absorb and foreign particles that also scatter. Calorimetry requires 10‐30 min but measures cell numbers in opaque samples impossibl

ISSN:0006-3592    

DOI:10.1002/bit.260350102

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

年代:1990

数据来源: WILEY

摘要:

AbstractA fast inferential, multivariable adaptive optimization algorithm based on a fast responding off‐gas data, the carbon dioxide evolution rate (CER), has been developed and applied to a continuous baker's yeast culture to maximize the cellular productivity in simulation and experimental studies. In the simulation study the process was optimized based on CER measurements using readily available steady‐state data on the ratio between the cellular productivity and the CER. It was shown that the algorithm is two to three times faster than the algorithm based on cell mass concentration measurements. In the experimental study the CER was maximized without any information on the relationship between the cellular productivity and the CER. It took about 40 h for the process to converge, while about 80 h was required when the optimization was based on cell mass measurements. The attained steady state was found to be different but fairly close to that obtained with cell measurements. Briefly discussed is a switching to the cell‐mass‐based algorithm at the final stage of the optimization to overcome a potential ina

ISSN:0006-3592    

DOI:10.1002/bit.260350103

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

年代:1990

数据来源: WILEY

摘要:

Abstractα‐Galactosidase from soybean (Glycine max) was purified by a five‐step procedure. The enzyme's natural substrates, raffinose and stachyose, haveKm's of 3. 0 mMand 4. 79 mM, respectively. The products, galactose and sucrose, were measured after separation by liquid chromatography. Galactose is a competitive product inhibitor of stachyose and raffinose hydrolysis with aKiof 0. 12 mM.We determined these parameters by an integral kinetic approach. Stachyose hydrolysis gives a nearly constant level of raffinose shortly after hydrolysis begins. Thus, cleavage of the first α‐(1,6)‐bond in the tetrasaccharide is the rate‐limiting step. Since the stachyose hydrolysis yields raffinose, soybean α‐galactosidase simultaneously hydrolyzes two substrates. We present a novel approach for analyzing simultaneous substrate hydrolysis with competitive product inhibition by a modified integral rate expression. The experimentally found kinetic parameters are confirmed by solving the simultaneous equations which describe the hydrolysis. This technique may be applicable to other hydrolytic enzymes with multi

ISSN:0006-3592    

DOI:10.1002/bit.260350104

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

年代:1990

数据来源: WILEY

摘要:

AbstractCellular plasmid content determines the yield of closed‐gene product, affects plasmid replication, and influences the behavior of the culture by dictating the extent of metabolic burden on the host cell and plasmid segregation at cell division. Hence, it is a variable of primary importance in the study of recombinant cell cultures. In this article, equations are developed to enable the conversion of experimental determinations of cellular plasmid content into theoretically important units. The importance of different units in characterizing plasmid effect on cell response is highlighted. Also, equations that relate cellular plasmid content to cloned‐gene expression are developed and successfully tested on several sets of data from literat

ISSN:0006-3592    

DOI:10.1002/bit.260350105

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

年代:1990

数据来源: WILEY

摘要:

AbstractA model is proposed for enzymatic lysis of microbial cells based on number balances over the distribution of cell‐wall mass in a population of cells. Analytical solutions to the population balance equations were obtained by the method of characteristics for simple reaction kinetics. The model has been used to analyze the following cases of lysis in a nonhomogeneous cell population: wall hydrolysis with cell rupture and product release, the effect of a distribution of lysis rates, and lysis of two‐layer cell walls. Rate expressions for the reactions of lysis can be derived from bulk‐phase experiments; the distributions of cell size and product content can be measured independently by flow cytometric techniques. The population model also provides an explanation for the initial lag seen in lysis kinetics for virtually any initial distribution. The model demonstrates patterns of lysis and product recovery for heterogeneous populations of cells and also applies to the more general problem of soluble‐enzyme reactions with heterogeneous solid sub

ISSN:0006-3592    

DOI:10.1002/bit.260350106

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

年代:1990

数据来源: WILEY

摘要:

AbstractMeasurements ofkLa were carried out in 1. 5‐ and 5‐L New Brunswick Scientific CelliGen® bioreactors. The measuredkLa in water were identical for both vessel sizes operated in similar condition. The mass transfer rate increased with temperature, mixing speed, and aeration rate, with this last parameter being the most significant. Surface aeration alone gavekLa values of 0. 4 to 1. 6 h−1. A 25% decrease inkLa was observed above an aeration rate of 1. 6 vvm. This was caused by the particular foam breaker of the CelliGen bioreactor. Measurements ofkLa using a mammalian cell culture medium supplemented with 5% fetal calf serum (FCS) have confirmed the negative effect of the foam breaker onkLaThe measured value in this medium was 1. 2 h−1for all aeration rates, more than 60% of which was attributed to surface

ISSN:0006-3592    

DOI:10.1002/bit.260350107

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new biotechnological process for sulphide removal is proposed. The principle of this process is that sulphide is converted into elemental sulphur, which can be removed by sedimentation. In this article, investigations on the optimization of the sulphur production are reported. It seems that less than 10% sulphate is produced at low oxygen concentration, when the sulphide concentration in the reactor exceeds 10 mg/L. At sulphide concentrations higher than 20 mg/L only 5% of the incoming sulphide is converted to sulphate even at high oxygen concentrations. An immobilized biomass on recticulated polyurethane produced more sulphate than a free cell suspension at the same oxygen and sulphide concentration.

ISSN:0006-3592    

DOI:10.1002/bit.260350108

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

年代:1990

数据来源: WILEY

摘要:

AbstractRelatively large activated sludge floes (larger than about 100 μm) were stabilized, using a histological tissue specimen preparation procedure, and then were sliced into sections of 3 to 6 μm thick. The study of these sections, after staining, revealed the internal structure of the activated sludge floes. No uniformity of this structure was found. The distribution of microorganisms and of extracellular polymers (EPs) in the floes varied randomly on the plane of the sections and along the dimension perpendicular to the plane, leaving large water channels and reservoirs in some of the floes. The lack of a characteristic size for the water gaps in the floes and a general self‐similar appearance of the sections suggested that the activated sludge floes might be characterized by the fractal concept within a certain size limit. Direct observation of the interior of the floes indicated an abundant presence of extracellular polymers (EPs) in amorphous forms, surrounding microorganisms in most of the fl

ISSN:0006-3592    

DOI:10.1002/bit.260350109

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

年代:1990

数据来源: WILEY

摘要:

AbstractViable hybridoma cells were encapsulated. The capsules were formed in one step by placing a drop of cell suspension mixed with negatively charged carboxymethylcellulose (CMC) into a positively charged chitosan solution through the interpolymeric ionic interaction between two oppositely charged polymers. These capsules were found to have a mean diameter of about 1. 5 mm and wall thickness of 3 μm. The cells grew in the capsules using supplemented DMEM/F12 (four kinds of growth factor). The maximum cell density in encapsulating cell culture reached 1 × 107cells/ml, 10 times higher than that obtained in the free cell culture. The maximum monoclonal antibody concentration in the free cell culture was 15μg/mL, but that in the capsule was 45μg/mL The antibody produced by the cell was concentrated about four times higher inside than outside of the capsu

ISSN:0006-3592    

DOI:10.1002/bit.260350110

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

年代:1990

数据来源: WILEY

摘要:

AbstractA major cost consideration in the use of anaerobic digestion to convert biomass and waste to utility‐grade gas is the expense of separating CO2from the product gas. Anaerobic digestion has a number of inherent properties that can be exploited to increase the methane content of the gas directly produced by the digester, the most important of which is the high solubility of CO2(40‐60 times that of methane) in water under digestion conditions. The methane enrichment concept examined in this study involved the recirculation of a liquid stream from the digester through a CO2desorption process and the return of the liquid stream back to the digester for absorption of additional CO2produced by the conversion of organic materials. A steady‐state equilibrium model predicted that a digester gas methane content exceeding 94% could be achieved with this scheme using modest recirculation rates provided a desorption process could be designed to achieve a 60+% CO2removal efficiency in the degassing of the liquid recycle stream. Using fixed‐film laboratory digesters operated on synthetic feedstocks, the technique of methane enrichment was tested under pressurized and unpressurized conditions. A 93 + 2% methane gas stream was produced from a volatile‐acid‐fed bench‐scale digester simulating the methanogenic stage of two‐phase digestion under conditions of (1) a pH swing achieved without caustic addition that allowed digestion at pH 7. 5 and air stripping at pH 6. 5‐7. 0, (2) digester pressurization to 30 psig, and (3) a recycle rate of 0. 33 L/L reactor/day. Significant but lower levels of methane enrichment were achieved with the single‐stage digester at the low experimental recycle rate. However, the narrow range among all experiments of CO2desorption efficiencies achieved in air stripping the recycle stream (35‐60% CO2removal) suggests that comparable methane enrichment‐may be achieved with unpressurized single‐stage digestion using greater recycle rates. A materials balance analysis of data from an unpressurized, single‐stage digester employing no chemical addition and using laboratory degassing efficiencies indicated that 94% methane could be produced at recycle rates of less than 1. 4 L/L reactor/day with a m

ISSN:0006-3592    

DOI:10.1002/bit.260350111

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

年代:1990

数据来源: WILEY