ISSN:0006-3592    

DOI:10.1002/bit.260480602

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe thermodynamics and energetics of the ion exchange of four amino acids at a cellulosic ion exchanger have been studied. Experimental work included determination of ion exchange isotherms and the use of high‐sensitivity titration microcalorimetry. A rigorous thermodynamic analysis of the data was developed allowing calculation of the standard free energy, the standard enthalpy, and standard entropy of exchange, and also the differential free energy, incremental enthalpy, and incremental entropy of exchange. The results show that the relative contributions of the enthalpy and entropy to the overall free energy differ markedly for the chosen amino acids. The reasons for these differences are analyzed and discussed. A knowledge of these fundamental thermodynamic properties indicates the solution conditions likely to give enhanced affinity of the ion exchanger for selected amino acids. The experimental techniques and analysis procedures developed are generally applicable to ion exchange separations of biomolecules. © 1995 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260480603

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

年代:1995

数据来源: WILEY

摘要:

AbstractA simple structured mathematical model coupled with a methodology of state and parameter estimation is developed for lipase production byCandida rugosain batch fermentation. The model describes the system according to the following qualitative observations and hypothesis: Lipase production is induced by extracellular oleic acid present in the medium. The acid is transported into the cell where it is consumed, transformed, and stored. Lipase is excreted to the medium where it is distributed between the available oil‐water interphase and aqueous phase. Cell growth is modulated by the intracellular substrate concentration. Model parameters have been determined and the whole model validated against experiments not used in their determination. The estimation problem consists in the estimation of three state variables (biomass, intra‐ and extracellular substrate) and two kinetic parameters by using only the on‐line measurement provided by exhaust gas analysis. The presented estimation strategy divides the complex problem into three subproblems that can be solved by stable algorithms. The estimation of biomass (X) and the specific growth rate (μ), is achieved by a recursive prediction error algorithm using the on‐line measurement of the carbon dioxide evolution rate. μ is then used to perform an estimation of intracellular substrate and the other kinetic parameter related to substrate transport (A) by an adaptive observer. Extracellular substrate is then evaluated by means of the estimated values of intracellular substrate and biomass through the material balance of the reactor. Simulation and experimental tests showed good performance of the developed estimator, which appears suitable to be used for process control and monitoring. © 1995 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260480604

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

年代:1995

数据来源: WILEY

摘要:

AbstractGelatine gels originate from water in oil microemulsions in which the ternary system consists of isooctane/ sulfosuccinic acidbis[2‐ethyl hexyl] ester/water; the solubilization of gelatin in the water pool of these microemulsions transforms them into viscous gels in which it is possible to cosolubilize various reactive molecules. These gels were used to immobilize two phenoloxidases, a laccase fromTrametes versicolorand a tyrosinase from mushroom. The best balance between gel retention and catalytic activity was reached at a gelatine concentration of 2.5% (w/v) in the case of tyrosinase, while laccase immobilization was independent of gelatine concentration. Both enzymes kept the same optimum pH as the corresponding soluble controls, while a partial loss of activity was observed when they were immobilized. Immobilized enzymes showed an increased stability when incubated for several days at 4°C with a very low release from the gels in the incubation solutions. The immobilization of tyrosinase and of laccase enhanced stability to thermal inactivation. Furthermore, gel‐entrapped tyrosinase was almost completely preserved from proteolysis: more than 80% of the activity was maintained, while only 25% of the soluble control activity was detected after the same proteolytic treatments. A column packed with gel‐immobilized tyrosinase was used to demonstrate that enzymes immobilized with this technique may be reused several times in the same reaction without loosing their efficiency. Finally, gel‐entrapped tyrosinase and laccase were capable of removing naturally occurring and xeno‐biotic aromatic compounds from aqueous suspensions with different degrees of efficiency. © 1995 John Wile

ISSN:0006-3592    

DOI:10.1002/bit.260480605

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of bioleaching of pyrite (FeS2) by the acidophilic thermophilic bacteriumAcidianus brierleyiwas studied in a well‐mixed batch reactor. Experiments were done at 65°C and pH 1.5 on adsorption ofA. brierleyionto pyrite particles, liquid‐phase oxidation of ferrous iron byA. brierleyi, and microbial leaching of pyrite. The adsorption ofA. brierleyiwas a fast process; equilibrium was attained within the first 30 min of exposure to pyrite. The adsorption equilibrium data were well correlated with the Langmuir isotherm. The oxidation of ferrous iron was markedly accelerated in the presence ofA. brierleyi, and the growth yield on ferrous iron was determined. The bioleaching of pyrite byA. brierleyiwas found to take place with a direct attack by adsorbed cells on the surface of pyrite, the chemical leaching of pyrite by ferric iron being insignificant. Rate data collected under a wide variety of operating variables were analyzed to determine kinetic and stoichiometric parameters for the microbial pyrite leaching. The specific growth rate on pyrite forA. brierleyiwas about four times that for the mesophilic bacterium,Thiobacillus ferrooxidans, whereas the growth yields on pyrite for the two microbes were approximately equal to one another in magnitude. A comparison ofA. brierleyiwithT. ferrooxidansfor pyrite leachability demonstrated the thermophile to be much more effective. © 1995 John Wiley&Sons

ISSN:0006-3592    

DOI:10.1002/bit.260480606

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe esterification of a long‐chain fatty acid was conducted using a nylon‐immobilized lipase fromCandida cylindraceain a nearly anhydrous, nonpolar organic medium, hexane. Butyl laurate was produced from lauric acid andn‐butanol at a maximum initial reaction rate of 37 mmol/h. g immobilized enzyme when the substrates were present in equimolar amounts at an initial concentration of 0.5 mol/L. Lower rates were obtained using nonstoichiometric amounts of the substrates. The rate of reaction increased with temperature, reaching a maximum between 35 and 45°C and decreasing sharply at higher temperatures. © 1995 John Wiley&So

ISSN:0006-3592    

DOI:10.1002/bit.260480607

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

年代:1995

数据来源: WILEY

摘要:

AbstractBased on the kinetics of Cr(VI) reduction byEscherichia coliATCC 33456 and phenol degradation byPseudomonas putidaDMP‐1, a mathematical model is developed to describe simultaneous Cr(VI) reduction and phenol degradation in the coculture of the two species. The developed model incorporates the toxicity effects of Cr(VI) and phenol on phenol degradation and Cr(VI) reduction in the coculture. The model illustrates the inhibitory effects of phenol on Cr(VI) reduction and Cr(VI) toxicity toward phenol degradation. The model also reveals the recoveries of the activities of the repressed bacterial cells with continuous Cr(VI) reduction and phenol degradation in the coculture. The model is capable of predicting simultaneous Cr(VI) reduction and phenol degradation within a broad range of Cr(VI) and phenol concentrations and under an appropriate composition of populations. However, the model simulates lower concentrations of phenol than experimental observations once Cr(VI) is reduced to a low level (<7 mg/L). The model simulation for Cr(VI) also deviates from experimental data whenP. putidais outnumbered byE. coliby a ratio of 1:5. © 1995 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260480608

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

年代:1995

数据来源: WILEY

摘要:

AbstractTwo thermophilic bacteria,Thermus aquaticusATCC 25104 andThermusspecies ATCC 27978, were investigated for their abilities to degrade BTEX (benzene, toluene, ethylbenzene, and xylenes).Thermus aquaticusand theThermussp. were grown in a nominal medium at 70°C and 60°C, respectively, and resting cell suspensions were used to study BTEX biodegradation at the same corresponding temperatures. The degradation of BTEX by these cell suspensions was measured in sealed serum bottles against controls that also displayed significant abiotic removals of BTEX under such high‐temperature conditions. ForT. aquaticusat a suspension density of only 1.3 x 107cells/mL and an aqueous total BTEX concentration of 2.04 mg/L (0.022mM), benzene, toluene, ethylbenzene,m‐xylene, and an unresolved mixture ofo‐andp‐xylenes were biodegraded by 10, 12, 18, 20, and 20%, respectively, after 45 days of incubation at 70°C. For theThermussp. at a suspension density of 1.1 x 107cells/mL and an aqueous total BTEX concentration of 6.98 mg/L (0.079mM), benzene, toluene, ethylbenzene,m‐xylene, and the unresolved mixture ofo‐andp‐xylenes were biodegraded by 40, 35, 32, 33, and 33%, respectively, after 45 days of incubation at 60°C. Raising the BTEX concentrations lowered the extents of biodegradation. The biodegradations of both benzene and toluene were enhanced whenT. aquaticusand theThermussp. were pregrown on catechol ando‐cresol, respectively, as carbon sources. Use of [U‐14C]benzene and [ring‐14C]toluene verified that a small fraction of these two compounds was metabolized within 7 days to water‐soluble products and CO2by these nongrowing cell suspensions. Our investigation also revealed that the nominal medium can be simplified by eliminating the yeast extract and using a higher tryptone concentration (0.2%) without affecting the growth and BTEX degrading activities of these cells. ©

ISSN:0006-3592    

DOI:10.1002/bit.260480609

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe biodegradation of nitrobenzene was attempted by usingPseudomonas putidaTB 103 which possesses the hybrid pathway combining thetodand thetolpathways. Analysis of the metabolic flux of nitrobenzene through the hybrid pathway indicated that nitrobenzene was initially oxidized tocis‐1,2‐dihydroxy‐3‐nitrocyclohexa‐3,5‐diene by toluene dioxygenase in thetodpathway and then channeled into thetolpathway, leading to the complete biodegradation of nitrobenzene. A crucial metabolic step redirecting the metabolic flux of nitrobenzene from thetodto thetolpathway was determined from the genetic and biochemical studies on the enzymes involved in thetolpathway. From these results, it was found that toluate‐cis‐glycol dehydrogenase could convertcis‐1,2‐dihydroxy‐3‐nitrocyclohexa‐3,5‐diene to catechol in the presence of NAD+with liberation of nitrite and the reduced form of NAD+(NADH) into the medium.

ISSN:0006-3592    

DOI:10.1002/bit.260480610

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

年代:1995

数据来源: WILEY

摘要:

AbstractIn order to study and control fermentation processes, indirect on‐tine measurements and mathematical models can be used. In this article we present a mathematical on‐line model for fermentation processes. The model is based on atom and partial mass balances as well as on equations describing the acid‐base system. The model is brought into an adaptive form by including transport equations for mass transfer and unstructured expressions for the fermentation kinetics. The state of the process, i.e., the concentrations of biomass, substrate, and products, can be estimated on‐line using the balance part of the model completed with measurement equations for the input and output flows of the process. Adaptivity is realized by means of on‐line estimation of parameters in the transport and kinetic expressions using recursive regression analysis. These expressions can thus be used in the model as valid equations enabling prediction of the process. This makes model‐based automation of the process and testing of the validity of the measurement variables possible. The model and the on‐line principles are applied to a 3.5‐L laboratory tormentor in whichSaccharomyces cerevisiaeis cultivated. The experimental results show that the model‐based estimation of the state and the predictions of the process correlate closely with high‐performance liquid chromatography (HPLC) analyses. © 1995

ISSN:0006-3592    

DOI:10.1002/bit.260480611

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

年代:1995

数据来源: WILEY