摘要:

AbstractThe design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.

ISSN:0006-3592    

DOI:10.1002/bit.260330402

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

年代:1989

数据来源: WILEY

摘要:

AbstractEscherichia coliharboring a recombinant plasmid was grown in a fermenter to study the effects of selected process parameters on the growth of the microbe and on plasmid amplification with chloramphenicol treatment. Eighteen fermentations were carried out according to a statistical experimental design in which the fermentation temperature, pH, and turbidity of culture at the onset of plasmid amplification were the selected independent process variables. Static regression models describing the process were derived from the experimental results. It turned out that recombinant plasmid copy numbers could be influenced by controlling fermentation temperature and pH. The maximal copy number during bacterial growth phase and the optimal plasmid production were found to require fermentation conditions different from those needed for optimal bacterial growth and cell division. The conditions also differed significantly from those routinely used in research laboratories for plasmid preparation. The chloramphenicol treatment increased the plasmid copy number compared with chromosome numbers up to fivefold. Some of the data suggest that under certain conditions the number of chromosome molecules inE. colicells may rise during the plasmid amplification stage. Statistical experimental design, a nucleic acid sandwich hybridization technique for plasmid quantification, and regression models proved to be useful in this study.

ISSN:0006-3592    

DOI:10.1002/bit.260330403

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

年代:1989

数据来源: WILEY

摘要:

AbstractRate and yield expressions relating to biomass and xanthan formation and to nitrogen, glucose, and oxygen consumption were established forXanthomonas campestrisbatch fermentations in a bubble column. Microbial growth was described by the logistic rate equation, characterized by a maximum specific growth rate μM= 0.5 h−1and a maximum attainable cell concentration provided by nitrogenous compounds. With regard to carbon metabolism, the decrease with time in experimental yields and in the experimental specific rates of xanthan production and glucose assimilation demonstrated the inadequacy of the Luedeking–Piret model. These decreases were connected to the simultaneous drop in dissolved‐oxygen tension observed during xanthan synthesis. The knowledge of metabolic pathways and energetic balance were used to establish the relationships between substrate utilization, ATP generation, and xanthan production. The model was structured by assuming the oxygen limitation of both the respiration rate and the efficiency of the oxidative phosphorylation mechanism (P/O ratio). Consequently, the specific rates and yield expressions became dependent on the dissolved‐oxygen tension, i.e., of the volumetric oxygen transfer in the f

ISSN:0006-3592    

DOI:10.1002/bit.260330404

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

年代:1989

数据来源: WILEY

摘要:

AbstractAerobic glucose metabolism byPseudomonas aeruginosabiofilms at various calcium loading rates was investigated. The influence of calcium on specific growth rate, extracellular polymeric substance (EPS) formation rate, biofilm detachment rate, and biofilm calcium concentrations was determined. Calcium accumulated in the biofilm in proportion to the liquid phase concentration. Increasing calcium concentration increased the cohesiveness of the biofilm as indicated by a lower relative detachment rate. Specific activity in the biofilm was the same as that measured in a chemostat and was not influenced by changing calcium concentration. EPS formation rate in the biofilm was unaffected by calcium concentration but was higher than that observed in a chemostat.

ISSN:0006-3592    

DOI:10.1002/bit.260330405

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe transient response method is introduced to elucidate the mechanism of reaction over immobilized enzyme. Glucose oxidation over the glucose oxidase that was immobilized on ion‐exchange resin using glutaraldehyde as a linking agent is selected as an example here. The transient responses of a fixed‐bed reactor to step increases and decreases in glucose, oxygen, and gluconolactone feed concentrations have been monitored and interpreted. From some responses, we have found that gluconolactone is formed in the reaction of glucose with adsorbed oxygen, while hydrogen peroxide is formed in the reaction of oxygen with adsorbed glucose. Combining all information from interpreting the responses with the literature, a mechanistic picture can be obtained as follows:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {E_{{\rm ox}} + G \to E_{{\rm red}} GL} \\ {E_{{\rm red}} GL \to E_{{\rm red}} + GL} \\ {E_{{\rm red}} + {\rm O}_2 \to E_{{\rm ox}} {\rm H}_2 {\rm O}_2 } \\ {E_{{\rm ox}} {\rm H}_2 {\rm O}_2 \to E_{{\rm ox}} + {\rm H}_2 {\rm O}_2 } \\ \end{array} $$\end{docume

ISSN:0006-3592    

DOI:10.1002/bit.260330406

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe saccharification of the polysaccharides of barley, oat, and wheat straws and Solka Floc was studied using the extracellular enzyme system synthesized by mutant strain NTG III/6 of the fungusPenicillium pinophilum87160iii. The enzymes obtained in cultures containing Solka Floc or barley straw as the carbon source were compared. Solka Floc at 10% (w/v) concentration was hydrolyzed to the extent of 70% in 72 h at 50°C using a reaction mixture containing 7 filter paper units/mL of cellulase induced on Solka Floc, but hydrolysis was increased to 90% when the enzyme induced on barley straw was used. Under the same conditions, the polysaccharides in barley, oat, and wheat straws were hydrolyzed, respectively, in 72 h, to the extent of 42–48%, 62%, and 52%, but hydrolysis was increased to 93%, 100%, and 92%, respectively, after treatment of the substrates with alkaline‐H2O2reagent at room tempera

ISSN:0006-3592    

DOI:10.1002/bit.260330407

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe oxidation of Fe2+with oxygen in sulfate solutions was studied in the presence ofT. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+<0.001M,T<25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression:\documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm Fe}^{2 + }]}}{{dt}} = 1.62 \times 10^{11} C_{{\rm bact}} [{\rm H}^ + ][{\rm Fe}^{2 + }]p{\rm O}_2 e^{ - (58.77/RT)} $$\end{document}Below pH = 2.2, the oxidation rate is independent of H+Concentration

ISSN:0006-3592    

DOI:10.1002/bit.260330408

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe growth rate of the hybridoma cell line ATCC‐CRL‐1606 in low serum medium declines rapidly with time after inoculation. To characterize this phenomenon, the stability of the growth‐promoting activity of serum was investigated. The activity of serum was found to de grade with time, and was stabilized by alterations in the medium formulation that acted to lower the oxidation/reduction potential. This included both the addition of thiols and the elimination of disulfides from the medium. Additionally, cysteine and other thiols were shown to stimulate growth in low serum, low cell density cultures, suggesting that thiols may be rate‐limiting in low serum medium. Stimulation of growth by thiol addition was less significant at high cell levels, implying that the cells themselves may be acting to reduce their environment. A hypothesis is presented based on these results which suggests that the actual rate‐limiting moieties in low serum cultures may be

ISSN:0006-3592    

DOI:10.1002/bit.260330409

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

年代:1989

数据来源: WILEY

摘要:

AbstractA simple procedure is developed to process experimental data from plasmid maintenance studies of recombinant cells in a chemostat with nonselective medium. This procedure, based on the model proposed by Imanaka and Aiba, provides quantitative information on the rate of plasmid loss and the difference in the specific growth rate between the plasmid‐carrying and plasmid‐free cells. The performance of the proposed method is evaluated through simulation studies. In addition, the method is applied to a set of previously reported experimental data. The two‐parameter model, together with the estimated parameter values, provides an excellent fit to the experimental

ISSN:0006-3592    

DOI:10.1002/bit.260330410

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

年代:1989

数据来源: WILEY

摘要:

AbstractIt is well established that pure and simple microbial competitors cannot coexist at a steady state if their environment is homogeneous. For the case of two microbial populations competing purely and simply in two interconnected chemostats having time‐invariant input(s), it is known from the literature that a stable steady state of coexistence arises in domains of the operating parameters space and is attributed to the spatial heterogeneities of the system, which allow a different species to have the competitive advantage in each one of the two sub‐environments. This article investigates whether the aforementioned result can be extended to the case of three species competing in three interconnected vessels. By studying all possible alternate configurations of the three‐chemostat system, it is shown that coexistence of the three species is impossible, except possibly for some discrete values of the operating parameters. Some potential explanations for the results are disc

ISSN:0006-3592    

DOI:10.1002/bit.260330411

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

年代:1989

数据来源: WILEY