摘要:

AbstractData reported here and previously indicate that when dextrin is hydrolyzed in the presence of immobilized glucoamylase, use of a larger average molecular weight substrate leads to lower overall rates of hydrolysis, while the maltose concentration during the bulk of the reaction and the maximum glucose concentration are lower than when the soluble form of the enzyme is employed under the same conditions. Computer simulation of the system demonstrated that all three observations were caused by pore diffusion limitation: the first by slow diffusion of substrate, the second by slow diffusion of intermediates, and the third by slow diffusion of glucose. Follow‐up experiments with glucoamylase immobilized to particles of different sizes confirmed this finding, as results with the smallest beads were identical to those with soluble glucoamylas

ISSN:0006-3592    

DOI:10.1002/bit.260220102

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

年代:1980

数据来源: WILEY

摘要:

AbstractA process is described in which the baboon endogenous virus (BaEV) is produced under optimum conditions in cell culture, and concentrated by hollow‐fiber ultrafiltration technology under conditions of large‐scale production. This system has advantages over conventional systems in that the flow rate is increased 2.5‐fold during concentration. Thermal inactivation of BaEV was retarded by the addition of lactose glutamate to the harvested tissue culture fluid. After concentration, at least 91% of the virus RNA‐directed DNA polymerase is recovered with a concomitant increase in infectious virus. Materials needed for modifying described systems may be obtained from commercial

ISSN:0006-3592    

DOI:10.1002/bit.260220103

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

年代:1980

数据来源: WILEY

摘要:

AbstractA simple model is developed for the energy transformation in growing microbial systems. The model is based on a linear equation for ATP consumption in the processes of growth and maintenance. A combination of this equation with macroscopic balances for the various components, the systems exchanges with the environment, and application of the concepts of the elementary balance allow the derivation of linear equations for the exchange of substrate, oxygen, and carbon dioxide with the environment. For growth on one sole carbon and energy source the model allows the definition of a critical substrate yield are expected and below which is decreasing substrate yield and energy supply growth limitation are expected. This restriction can be interpreted in a variety of other ways. It supplies a rationale for non‐energy‐production‐coupled transfer of hydrogen to oxygen or wasteful expenditure of ATP in growth on highly reduced substrates. It also allows the formulation of a limit to the maximum yield on oxygen that can never be exceeded in growth on highly reduced subst

ISSN:0006-3592    

DOI:10.1002/bit.260220104

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe phosphodiesterase from calf spleen (EC 3.1.4.18) was immobilized on several supports. Some properties of the most suitable enzyme support system—calf spleen phosphodiesterase bound to agarose‐Concanavalin A—were investigated, e.g., pH dependence, influence of ionic strength of the buffer medium, and Zn2+‐ion inhibition. The immobilized spleen phosphodiesterase showed about 60% of the activity of the free enzyme: the activity toward several oligonucleotide test substrates was unchanged for two

ISSN:0006-3592    

DOI:10.1002/bit.260220105

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

年代:1980

数据来源: WILEY

摘要:

AbstractThis research examined culture parameters influencing the rate of degradation of lignin in lignocellulosic substrates by the BasidiomycetePhanerochaete chrysosporium.Thermomechanical pulps prepared from western hemlock (Tsuga heterophylla) and red alder (Alnus rubra) were chosen as model substrates. Degradation of lignin in shallow, liquid‐phase, stationary cultures was 10 times as rapid as in agitated cultures. Lignin degradation was at least 50% more rapid in cultures under 100% O2than in those under air. Addition of 0.12% nutrient N (dry pulp basis) increased the rate of lignin degradation two‐ to fivefold; 1.2% added N at first suppressed, then stimulated, lignin degradation. Lignin in the alder pulp was degraded over five times as rapidly as in the hemlock pulp. Addition of glucose (35% of dry pulp) to the pulps containing 0.12% added N completely suppressed polysaccharide depletion during two weeks, but did not influence lignin degradation. The maximum rate of lignin degradation was 3%/day over a two‐week incubation, or approximately 2.9 mg/mg fungal cell protein/day. The influence of the examined parameters was in complete accord with those found earlier for synthetic14C‐lignin metabolism byP. chryso

ISSN:0006-3592    

DOI:10.1002/bit.260220106

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

年代:1980

数据来源: WILEY

摘要:

AbstractA procedure for large‐scale preparation of a lectin fromCrotalaria junceaseeds is described. The method involve fractionation by pH‐ and ammonium sulfate precipitation followed by biospecific affinity chromatography. The adsorbent used for the affinity chromatography was prepared by coupling galactose to Sepharose 6B activated with divinylsulfone. A comparison of different apparatus and techniques involved in the preparation is discussed. The yield and quality of the lectin prepared at a large scale were comparable with laboratory‐scale preparation. From 50 kgCrotalaria junceabeans, 14.4 gCrotalarialectin were obt

ISSN:0006-3592    

DOI:10.1002/bit.260220107

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

年代:1980

数据来源: WILEY

摘要:

AbstractThree feedback strategies for the on‐line control of cell densities in a mixed‐culture system have been examined. A competitive mixed‐culture system ofCandida utilisandCorynebacterium glutamicumgrown on glucose as the limiting carbon source was modeled using Monod growth kinetics. First‐order time constants were added to simulate transient growth effects. Multivariable feedback control of cell densities by manipulation of substrate feed and dilution rate was investigated. Feedback strategies directed to minimizing control interactions were found to be superior to classical feedback. Transients in the growth‐rate response produced oscillations in cell density and required retuning of control constants. The relative time constants of the two species were important, with the largest oscillations resulting when the faster growing organism had the faster time

ISSN:0006-3592    

DOI:10.1002/bit.260220108

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

年代:1980

数据来源: WILEY

摘要:

AbstractStudies were made of the death kinetics ofEscherichia colicells heated at 46 to 56°C in 0.05Mphosphate buffer (pH 7.0) containing either an amphoteric surfactant (Tego 15DL, 1–10 μg/ml) or sorbic acid (0.5 to 3%). A linear relationship was obtained on the Arrhenius plot for the death of cells heated with each antimicrobial agent. The kinetics of the action of the surfactant, however, differed from that of sorbic acid. With the amphoteric surfactant, the activation enthalpy of the death reaction decreased from 108 to 51 kcal/mol as the concentration of surfactant was increased in the range tested although the death rate remained high; whereas with sorbic acid the activation enthalpy remained fairly constant (104 ± 9 kcal/mol) independent of its concentration and the death rate was similarly high. Further, in the action of the amphoteric surfactant, a thermodynamic compensation effect was observed, the compensation temperature being 334°K (61°C), i.e., relatively close to the observed temperatures. For sorbic acid, however, this temperature seemed to be too high to observe when determined from the Arrhenius plot. The data of the dependency of the death‐rate constant upon the concentration of antimicrobial agent indicated a similar difference in the action of the two agents. Based on our results and on data obtained by other workers, we propose that antimicrobial agents that enhance cellular death induced by heating can be characterized into t

ISSN:0006-3592    

DOI:10.1002/bit.260220109

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe steroid transformation of hydrocortisone to prednisolone, combining the two techniques of immobilized whole cells and high steroid concentrations, was investigated and found to be a feasible process. Freeze‐driedCorynebacterium simplexcells were immobilized in collagen, tanned with glutaraldehyde, and cast into a membrane. The reaction was studied at hydrocortisone concentrations ranging from 5 to 50 mg/ml. The following aspects of the system were examined: (1) the substrate concentration effect upon the reaction; (2) the effect of enzyme concentration; (3) the rate‐concentration relationship; and (4) the product inhibition characteristics of the system. The optimal substrate concentration was found to be 15 mg/ml of a membrane concentration of 80 mg/ml. This reaction attained an 80% conversion in 48 hr. A liner relation was found between the initial reaction rate and membrane concentration. One can thus increase the net production of steroid per unit volume and time by increasing the membrane levels. A physical limit to this increase occurred at membrane concentrations greater than 125 mg/ml. The rate‐concentration relationship was linear when graphed on a Line weaver‐Burk plot: giving aKm′ andVm′ value of 5.39 mg/ml and 0.556 mg/ml/hr, respectively. When the data were tested for competitive product inhibition, the curves fitted the experimental points fairly well and producedKm′ andVm′ values of 4.52 mg/ml and 0.566 mg/ml/hr, respectively. Product inhibition experiments showed that the inhibition was not purely competitive. At low substrate concentrations, product inhibited the enzyme; at high substrate concentrations, the enzyme was first stimulated and then depressed by increasing levels of products. This behavior has been analyzed and shown to be possibly a result of the information of a tertiary intermediate produced duri

ISSN:0006-3592    

DOI:10.1002/bit.260220110

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

年代:1980

数据来源: WILEY

摘要:

AbstractMany changes that occur in a cell during the cell cycle can be demonstrated in synchronous cultures and can reveal dimensions of cell metabolism not attainable by the study of balanced growth of asynchronous populations in batch cultures or the steady state in chemostat cultures. The release of14CO2from specifically labeled glucose by phased (continuously synchronized) cultures follows a characteristic pattern (profile) that depends upon the stage in the cell cycle and the period of labeling used. Successive profiles throughout a cycle showed differences that were altered under different nutrient‐limiting growth conditions. Profiles obtained with glucose‐1‐14C, glucose‐2‐14C, glucose‐3,4‐14C, and glucose‐6‐14C and phased cells ofCandida utilisunder N‐, P‐, and C‐limited growth demonstrated the variable character of the metabolic activity that occurred in the cells while contour changes within the profiles across the cycle indicated possible correlations with activities of the hexose monophosphate, Embden‐Meyerhof‐Parnas, and tricarboxylic acid cycle pathways during the cell cycle. The basis of these changes and their use as elementary parameters for study of problems of physiological c

ISSN:0006-3592    

DOI:10.1002/bit.260220111

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

年代:1980

数据来源: WILEY