摘要:

AbstractA cephalosporin acetylesterase produced byBacillus subtiliscatalyzes the deacetylation of 7‐aminocephalosporanic acid (7‐ACA). Previous reports from our laboratory described the kinetic constants that characterize the reaction:Km= 2.8 × 10−3M,Kiaacetate = 5 × 10−2M, andKiddeacetyl‐7‐ACA = 3.6 × 10−2M. These constants were used to predict the time course of the reaction using the following equation for dual competitive product inhibition.\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dS_t}}{{dt}} = \frac{{- V_{\max}}}{{1 + \left({K_m /S_t} \right)\left({1 + A_t /K_{{\rm ia}} + D_t /K_{{\rm id}}} \right)}} $$\end{document}whereSt= mg/ml 7‐ACA,At= mg/ml acetate,Dt= mg/ml deacetyl‐7‐ACA. The predicted time course closely matched the time course measured experimentally. The equation also was solved without the inhibition terms and the solution indicated that product inhibition caused about a 30% increase in the time required for complete (>97%) hydrolysis of a 24 mg/ml 7‐ACA solution. The esterase was immobilized by containment within an ultrafiltration device. With this technique the enzyme was reused 20 times over an 11 day span to deacetylate 7‐ACA solutions containing 4 to 24 mg/ml 7‐ACA. The specific activity after the 20th use was the same as the activity prior to the first use, indicating little

ISSN:0006-3592    

DOI:10.1002/bit.260180802

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

年代:1976

数据来源: WILEY

摘要:

AbstractA mathematical model is suggested for growth of microorganisms under limitation by “conservative” substrates such as inorganic ions or vitamins that are not broken down after uptake into the cells, but that wholely or partly remain available for production of biomass. The specific growth rate is expressed here as a function of the intracellular “concentration” of the limiting substrate, defined as the amount of substrate within the cells per unit of cell dry weight.In the model, the intracellular substrate is divided into two parts. One part is a “structural” substrate not available for further growth. The other part is an “excess” or “functional” substrate that is used for biomass production and is assumed to be converted into structural substrate proportionally to growth. The rate of growth is believed to be controlled by the intracellular concentration

ISSN:0006-3592    

DOI:10.1002/bit.260180803

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

年代:1976

数据来源: WILEY

摘要:

AbstractFlow system technology enables the biological and medical experimenter to investigate the distribution spectra of various cellular characteristics separately or in parameter combination on the basis of ultrarapid single cell measurements. A typical rate of recognition is about 1000 to 5000 cells per second and the precision of measurements and their statistical relevance has been previously unobtainable. According to the approach of the multiparameter analysis and high data rate, computer assistance in flow system technology is given primary consideration. In this study three different kinds of software controlled modes in data acquisition are demonstrated: normal acquisition and linear accumulation of single parameters, spectra accumulation of two correlated parameters of each single cell and documentation as linear, two‐ or three‐dimensional distribution pattern, and linear accumulation of two correlated parameters simultaneously with their actual signal‐to‐signal ratio. A first attempt to analyze distribution spectra was the application of the entropy of the structure routinely used in cybernetics. This function seems to be a measure for determining the degree of synchrony in an appropriate pretreated cell population. A special mathematical strategy has been applied to the linear spectra of cellular DNA content, whose advantage is the quantitative extraction of the fractions concerning the various phases of the life cycle cells. The validity of this special curve fitting procedure has been proven on various experimental cell popu

ISSN:0006-3592    

DOI:10.1002/bit.260180804

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe design of a continuous multistage tower fermentor is described. The fermentor consists of five stages separated by perforated plates. Each stage includes mechanical mixing provided by two disc turbine impellers and has its own impeller shaft with bearing assembly and flexible coupling that enables the operation of an arbitrary number of stages. The normal operation of this system enables the co‐current flow of gas and liquid, but the system can function countercurrently as well.The purpose of this study was to examine the hydrodynamic performance, i.e., the pressure gradient along the tower, the mixing time, gas holdup, the residence lime distribution of the continuous phase, the value of the backflow coefficient, and the oxygen transfer rate under conditions usually used during fermentations. From the interrelations between parameters influencing the proper performance of this system, an optimal design of plate geometry for processes requiring high oxygen transfer rate was formulate

ISSN:0006-3592    

DOI:10.1002/bit.260180805

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe microbiological leaching of a chalcopyrite concentrate has been investigated using a pure strain ofThiobacillus ferrooxidans. The optimum leaching conditions regarding pH, temperature, and pulp density were found to be 2.3, 35°C, and 22%, respectively. The energy of activation was calculated to be 16.7 kcal/mol. During these experiments the maximum rate of copper dissolution was about 215 mg/liters/hr and the final copper concentration was as high as 55 g/liter. This latter value is in the range of copper concentrations which may be used for direct electrorecovery of copper. Jarosite formation was observed during the leaching of the chalcopyrite concentrate. When the leach residue was reground to expose new substrate surface, subsequent leaching resulted in copper extractions up to about 80%. On the basis of this experimental work, a flow sheet has been proposed for commercial scale biohydrometallurgical treatment of high‐grade chalcopyrite materia

ISSN:0006-3592    

DOI:10.1002/bit.260180806

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe biosynthesis of invertase bySaccharomyces carlsbergensisLAM 1068 was studied in relation to its glucose effect at both unsteady and steady states of growth. Experimental correlations between the dilution rate and invertase specific activity (E/X) in chemostat, cultures led to an optimum for the enzyme synthesis at a particular intermediate growth rate. The value ofE/Xincreased from 1.1 (U/mg biomass) in batch cultures to 13 (U/mg biomass) in chemostat cultures. A mutant strain A3 showed the highest value forE/X= 25 (U/mg biomass) at high dilution rates where glucose repression was observed with the wild strain.

ISSN:0006-3592    

DOI:10.1002/bit.260180807

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn a previous study on the chemostat culture ofSaccharomyces carlsbergensis, maximum invertase specific activity was observed at an intermediate dilution rate. A possible regulation mechanism, assuming there are simultaneous effects of induction and repression on two sites of the operator loci for invertase formation, is proposed which might account for the observed curve of the dilution rate effect.

ISSN:0006-3592    

DOI:10.1002/bit.260180808

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

年代:1976

数据来源: WILEY

摘要:

AbstractFive marine phytoplankton species (Phaeodactylum tricornutum, Thalassiosira pseudonana, Skeletonema costatum, Monochrysis lutheri, andDunaliella tertiolecta) were grown in enriched laboratory continuous cultures and natural populations were mass cultured outdoors for 16 months. Competition among the species was shown to be highly dependent on temperature, although the actual production of plant organic matter at the low growth rates used was relatively independent of this variable. Control of marine species in mass cultures does not appear economically feasible, but this drawback may be overcome by selecting herbivorous shellfish that are capable of assimilating those temperature‐dependent phytoplankton species dominating in a particular local

ISSN:0006-3592    

DOI:10.1002/bit.260180809

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

年代:1976

数据来源: WILEY

摘要:

AbstractVarious flavins, FMN, FAD, and acriflavin, were immobilized to Sepharose using several different coupling methods. The only product stable enough to permit extended studies was acriflavin coupled to epoxy‐substituted Sepharose. The nonenzymic oxidizing capacity towards NAD(P)H was investigated and a 25% specific activity, compared to that of free acriflavin, was observed. The reduced acriflavin was immediately auto‐reoxidized in air and could thus be reused. It was shown that acriflavin‐Sepharose preparations function as NAD(P)H oxidizing agents in a number of different dehydrogenase systems including lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), malate dehydrogenase (MDH), alanine dehydrogenase (alaDH), and glutamate dehydrogenase (GDH). The amount of expensive coenzyme necessary for high product formation of such systems was thereby markedly re

ISSN:0006-3592    

DOI:10.1002/bit.260180810

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

年代:1976

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260180811

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

年代:1976

数据来源: WILEY