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1.
The kinetic behavior of heterogeneous microbial populations was studied in a continuous flow completely mixed reactor operated at various dilution rates. Glucose was used as the growth-limiting nutrient. The physiological growth parameters for cells harvested from continuous flow reactors were determined using batch experiments. It, was found that the growth parameters, maximum growth rate (μ m), saturation constant ( ks), and cell yield ( Y) vary for each dilution rate, and cannot be considered as precise constants in depicting the kinetic behavior of heterogeneous populations. In addition, it was found that the yield coefficients obtained from batch experiments were always lower than those obtained from continuous flow experiments. Levels of substrate and biological solids calculated for different dilution rates using growth constants from batch experiments did not agree with the experimental values observed in steady-state experiments. However, when the yield values from, the continuous flow experiments were used in conjunction with batch values for μ m and ks the theoretical and experimental dilute-out curves agreed fairly closely (within the range needed for engineering prediction) until the culture began to wash out of the unit. In general, the data substantiated the use of the single phase relationship between growth rate and substrate concentration described by the Monod equation, μ = μ mS/( ks + s). 相似文献
2.
Summary Mycelia of Streptomyces sp. T 59-235 and Streptomyces tendae Tü 901 (producing the antibiotics tylosin and nikkomycin, resp.) were immobilized in different carriers. With both organisms best antibiotic production was observed in calcium alginate gel.Influence of aeration, cell density and flow rate on antibiotic production was investigated in batch fermentation and in a continuous system (air-bubbled reactor).In batch fermentation, immobilization prolongued the production phase from 72 to 120 h ( Streptomyces T 59-235) and from 72 to 96 h ( S. tendae). The relative productivity of immobilized cells was 40 to 50% compared to that of free mycelia in both cases.In continuous tylosin fermentation highest production rate was observed in a medium nearly saturated with oxygen.Nikkomycin production by immobilized S. tendae could be maintained for longer than 350 h in a continuous system. The production rate depended on cell density and flow rate of the medium. The maximum specific productivity was 100% compared to that of free mycelium in batch culture. 相似文献
3.
Summary Growth, sporulation, insecticidal crystalline protein (ICP) production and plasmids of Bacillus thuringiensis var. kurstaki (HD-1) were investigated during batch and continuous phased cultivation using a laboratory scale cyclone fermentor. When grown in batch culture at 28°C, 93% of the cells sporulated and produced ICP within 10 h of commencement of stationary phase. The batch culture runs were completed within 50 h of inoculation. A predominantly sporogenous and crystalliferous cell population was also obtained by second, stage processing of culture harvested from the first 10 to 25 cycles of continuous phased cultivation. In contrast, after 25 or more cycles of cultivation the population in the continuous phased culture shifted towards a predominantly asporogenous and acrystalliferous one. Culture conditions in continuous phased cultivation did not affect the plasmid content of B. thuringiensis (HD-1), yet influenced sporulation and plasmid-coded ICP production. 相似文献
4.
The behavior of Bifidobacterium animalis subsp. lactis Bb 12 under batch cultivation, after continuous culturing for up to 12 d, was monitored in skim milk-based media. Previous continuous culture for longer than 6 d affected the physiology of said microorganism. The minimum inhibitory concentrations of lactic and acetic acids increased from 18 to 26 g/l, whereas the molar ratio of acetic to lactic acid increased from 0.8 to 1.55, when the previous continuous culture increased its duration from 1 to 12 d. The specific lactose consumption rate decreased from 0.94 to 0.77 g lactose/g cell dry mass/h within the batch culture timeframe; this was concomitant with greater amounts of acetic and formic acids, and lower amounts of lactic acid produced. The β-galactosidase activity increased as continuous culturing time increased, and reached 446 units/ml by 12 d; however, the rate of enzyme synthesis decreased concomitantly. Succinic acid was produced during the exponential growth and stationary phases of the batch culture, but the former at exponential growth phase was higher as the continuous culturing time was longer. For comparison purposes, batch cultivation of samples taken from continuous cultures by 1 and 12 d was done using a semi-synthetic medium with glucose as carbon source; a pattern similar to that observed when using skim milk-based media was observed. 相似文献
5.
The design of an optimal process is particularly crucial when the reactants deactivate the biocatalyst. The reaction cascades of the chemo‐enzymatic epoxidation where the intermediate peroxy acid is produced by an enzyme are still limited by enzyme inhibition and deactivation by hydrogen peroxide. To avoid additional effects caused by interfaces (aq/org) and to reduce the process limiting deactivation by the substrate hydrogen peroxide, a single‐phase concept was applied in a fed‐batch and a continuous process (stirred tank), without the commonly applied addition of a carrier solvent. The synthesis of peroxyoctanoic acid catalyzed by Candida antarctica lipase B was chosen as the model reaction. Here, the feasibility of this biocatalytic reaction in a single‐phase system was shown for the first time. The work shows the economic superiority of the continuous process compared to the fed‐batch process. Employing the fed‐batch process reaction rates up to 36 mmol h ?1 per gram cat, and a maximum yield of 96 % was achieved, but activity dropped quickly. In contrast, continuous operation can maintain long‐term enzyme activity. For the first time, the continuous enzymatic reaction could be performed for 55 h without any loss of activity and with a space‐time yield of 154 mmol L ?1 h ?1, which is three times higher than in the fed‐batch process. The higher catalytic productivity compared to the fed‐batch process (34 vs. 18 g Prod g ?1cat) shows the increased enzyme stability in the continuous process. 相似文献
6.
Summary Living Aspergillus terreus cells were entrapped in polyacrylamide gels and employed in both replacement batch and continuous column reactors to produce itaconic acid from glucose.With the replacement batch reactor, maximum itaconic acid productivity was observed under the following conditions: pH 2.50, temperature at 35°C, addition of NH 4H 2PO 4 and MgSO 4·7H 2O. Using the continuous reactor, the maximum itaconic acid yield was 60 mg/h/40 g of gel. The biocatalyst activity or half-life was about 10 days. 相似文献
7.
In batch and continuous fermentations, the reduction in corrosion of SAE 1018 mild steel and 304 stainless steel caused by
inhibition of the reference sulfate-reducing bacterium (SRB) Desulfovibrio vulgaris by a protective, antimicrobial-producing Bacillus brevis biofilm was investigated. The presence of D. vulgaris produced a thick black precipitate on mild steel and a higher corrosion rate in batch cultures than that seen in a mono-culture
of non-antimicrobial-producing Pseudomonas fragi K upon the addition of SRB to the aerobic P. fragi K biofilm. In continuous reactors, the polarization resistance R
p decreased for stainless steel and increased for mild steel upon the addition of SRB to a P. fragi K biofilm. Addition of either 200 μg/ml ampicillin, chloramphenicol, or ammonium molybdate to batch and continuous reactors
after SRB had colonized the metal was ineffective in killing SRB, as inferred from the lack of change in both R
p and the impedance spectra. However, when ampicillin was added prior to SRB colonization, the growth of SRB was completely
inhibited on stainless steel in continuous reactors. Prior addition of ampicillin was only able to delay the growth of SRB
on mild steel in continuous reactors. External addition of the purified peptide antimicrobial agent gramicidin S prior to
the addition of SRB also inhibited the growth of SRB on stainless steel in continuous reactors, and the SRB were also inhibited
on stainless steel in both batch and continuous reactors by producing gramicidin S in situ in a protective biofilm when the
gramicidin-S-overproducing strain Bacillus brevis 18 was used.
Received: 29 October 1998 / Received revision: 18 February 1999 / Accepted: 26 February 1999 相似文献
8.
Summary A thermophilic methanogenic bacterium, Methanococcus thermolithotrophicus, was grown on H 2 and CO 2 in both batch and continuous culture, in a fermentor equipped with either a straight blade impeller or a Rushton impeller. Production was continued until 470 l CH 4·l -1 per day was obtained with a biomass of 3.5 g dry wt. l -1 under batch conditions. 相似文献
9.
The effects of several natural antioxidants (copaiba oil, buriti oil, cocoa butter, tucuman butter, oregano and white thyme) were assessed in the enzymatic synthesis of monoglycerides (MAG) from the glycerolysis of babassu oil. The reactions were catalyzed by Burkholderia cepacia lipase immobilized on SiO2–PVA and the assays carried out in batch and continuous runs. Results were compared with those attained in the control reactions (without any strategy to avoid oxidation), and the best approach was tested in a continuous packed-bed reactor. The best performance was obtained using N 2 in the reaction medium (60 % of MAG) followed by buriti oil (57.6 % of MAG) and cocoa butter (56.6 % of MAG), preventing the oxidation of babassu oil in batch reaction. However, the incorporation of buriti oil in the medium influenced the MAG profile, leading to the largest formation of monoolein, unlike other runs. Similar results were obtained in continuous reactions, using inert atmosphere and cocoa butter (24–25 % of MAG). Thereby, among the tested antioxidant agents, cocoa butter was the most effective in both systems, because it did not interfere in the MAG profile and also reduced the cost of the process. 相似文献
10.
A budding coccoid bacterium, (CH1), a Vibrio sp. and a Pseudomonas sp. were investigated for factors governing their attachment to glass surfaces in static batch culture and laminar flow continuous culture systems. An analysis of variance showed that the three species exhibited very different responses. For CH1 attachment was dependent on cell density, incubation time and nutrient concentration. The Vibrio sp. was affected by nutrient concentration while the attachment of the Pseudomonas sp. was independent of cell density, incubation time and nutrient concentration. A comparison of attachment to hydrophilic and hydrophobic surfaces showed that attachment of the Vibrio sp. and CH1 to hydrophilic surfaces was 3 and 10 times greater respectively than to hydrophobic surfaces while Pseudomonas attached in equal numbers to both surfaces. The continuous culture system with defined flow hydrodynamics and growth conditions at steady state revealed a random sampling effect 3 times smaller than the batch culture system did. When the biofilm development of Pseudomonas sp. was followed during 46 h at different fluid shear under laminar and turbulent flow conditions, the former biofilm reached 3.3·10 8 cells·cm -2 and the latter 8.2·10 7 cells·cm -2.Non-common abbreviation NSS
Nine salt solution 相似文献
11.
The kinetic behavior of heterogeneous microbial populations of sewage origin was studied in a single-stage isothermal continuous flow completely mixed aeration tank. A series of experiments were carried out at various dilution rates using glucose as the growth limiting substrate. The steady-state behavior of the system was observed at each dilution rate and the results were found to fit fairly well with the steady-state equation bayed on the Monod model with an endogenous respiration term included, i.e., μ = μ mS/( Ks + S) ? Kd. The growth kinetics of cells harvested at steady state for each dilution rate were studied using batch experiments. The multiple response data of the system as functions of time were used to estimate the parameter values in the above kinetic model. It was found that values of the growth parameters changed significantly and systematically with cell population. For example, values of μ m were high at high dilution rates and low at low dilution rates. It was also found that only those batch growth parameters from cells obtained at fairly high dilution rates are comparable with those estimated by the results of steady-state operations. The results of this investigation suggest that (1) different cell populations pre dominated at different steady-state dilution rates, with high dilution rates resulting in predominantly fast-growing organisms and low dilution rates resulting in predominantly slow-growing cells, and (2) risk exists in any randomly picked batch experiment to predict the steady-state behavior of the system when heterogeneous microbial populations must be used. 相似文献
12.
A model that was used to describe toxicity from high concentrations of chlorinated aliphatic hydrocarbons (CAHs) on reductively dechlorinating cultures in batch reactors (Sabalowsky and Semprini (in press)) was extended here to simulate observations in continuous flow suspended and attached growth reactors. The reductively dechlorinating anaerobic Evanite subculture (EV‐cDCE) was fed trichloroethene (TCE) and excess electron donor to accumulate cis‐1,2‐dichloroethene (cDCE) in a continuous flow stirred tank reactor (CFSTR); and an attached growth recirculating packed column (RPC). A concentration‐dependent toxicity model used to simulate the results of batch reactors in part I (Sabalowsky and Semprini (in press) Biotechnol Bioeng) also simulated well the observations for the CFSTR and RPC growth modes. The toxicity model incorporates cDCE and TCE toxicity coefficients that directly increase the cell decay coefficient in proportion with cDCE and TCE concentrations. Simulated estimates of the cDCE and TCE toxicity coefficients indicate reductively dechlorinating cells are most sensitive to high concentrations of cDCE and TCE in batch‐fed growth, followed by CFSTR, with attached growth being least sensitive. The greater toxicity of TCE than cDCE, and ratio of the modeled toxicity coefficients, agrees with previously proposed models relating toxicity to partitioning in the cell wall ( KM/B), proportional to octanol‐water partitioning ( KOW) coefficients. Biotechnol. Bioeng. 2010;107: 540–549. © 2010 Wiley Periodicals, Inc. 相似文献
13.
Enrichment of n-3 polyunsaturated fatty acids from sardine cannery effluents upon enzymatic esterification by Lipozyme® was optimized in batch and in continuous processes. In these processes, the yield of docosahexaenoic acid (DHA) ( Y1) and the yield of eicosapentaenoic acid (EPA) ( Y2), in the residual acid fraction were maximized. In batch, a two-factor Doehlert design was used to study the effects of temperature and ratio of fatty acid to alcohol. Second order polynomial regression models for Y1 and Y2 were postulated to generate response surfaces. After esterification the fraction of fatty acid was enriched to 70% with DHA or to 44% with EPA. In a continuous process, a three-factor central composite design was employed to study the effects of temperature, ratio of fatty acid to alcohol and flow rate. Second order polynomial regression models for Y1 and Y2 were used to generate response surfaces. After esterification, a quantity of DHA close to 30% and 17% of EPA. 相似文献
14.
The oxidation and growth kinetics of ferrous iron with Thiobacillus ferrooxidans in continuous cultures was examined at several total iron concentrations. On-line off-gas analyses of O 2 and CO 2 were used to measure the oxygen and carbon dioxide consumption rates in the culture. Off-line respiration measurements in
a biological oxygen monitor (BOM) were used to measure directly the maximum specific oxygen consumption rate, qO 2,max, of cells grown in continuous culture. It was shown that these reproducibly measured values of qO 2,max vary with the dilution rate. The biomass-specific oxygen consumption rate, qO 2, is dependent on the ratio of the ferric and ferrous iron concentrations in the culture. The oxidation kinetics was accurately
described with a rate equation for competitive ferric iron inhibition, using the value of qO 2,max measured in the BOM. Accordingly, only the kinetic constant Ks/ K
i needed to be fitted from the measurements. A new method was introduced to determine the steady-state kinetics of a cell suspension
in a batch culture that only takes a few hours. The batch culture was set up by terminating the feeding of a continuous culture
at its steady state. The kinetic constant K
s/ K
i determined in this batch culture agreed with the value determined in continuous cultures at various steady states.
Received: 8 February 1999 / Accepted: 17 February 1999 相似文献
15.
Conversion of organic wastes to syngas is an attractive way to utilize wastes. The produced syngas can be further used to produce a variety of chemicals. In this study, a hollow-fiber membrane biofilm reactor with mix cultures was operated at 55 °C to convert syngas (H2/CO2) into acetate. A high concentration of acetate (42.4 g/L) was reached in batch experiment while a maximum acetate production rate of 10.5 g/L/day was achieved in the continuous-flow mode at hydraulic retention time (HRT) of 1 day. Acetate was the main product in both batch and continuous-flow experiments. n-Butyrate was the other byproduct in the reactor. Acetate accounted for more than 98.5 and 99.1% of total volatile fatty acids in batch and continuous modes, respectively. Illumina Miseq high-throughput sequencing results showed that microorganisms were highly purified and enriched in the reactor. The main genus was Thermoanaerobacterium (66% of relative abundance), which was usually considered as H2 producer in the literature, however, likely played a role as a H2 consumer in this study. This study provides a new method to generate the high producing rate and purity of acetate from syngas. 相似文献
16.
This study deals with the effects of the initial nitrogen source (NZ Case TT) level and the protocol of glucose addition during the fed‐batch production of tetanus toxin by Clostridium tetani. An increase in the initial concentration of NZ Case TT (NZ 0) accelerated cell growth, increased the consumption of the nitrogen source as well as the final yield of tetanus toxin, which achieved the highest values (50–60 L f/mL) for NZ 0 ≥ 50 g/L. The addition of glucose at fixed times (16, 56, and 88 h) ensured a toxin yield (~60 L f/mL) about 33% higher than those of fed‐batch runs with addition at fixed concentration (~45 L f/mL) and about 300% higher than those obtained in reference batch runs nowadays used at industrial scale. The results of this work promise to substantially improve the present production of tetanus toxin and may be adopted for human vaccine production after detoxification and purification. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 相似文献
17.
A pure culture of Pseudoinonas putida was grown in both a batch and continuous culture using phenol as the limiting substrate. Of two substrate inhibition models examined, the Haldane function was found to statistically best describe the kinetics. The applicable kinetic constants were either measured (μ M, KI) or estimated ( KS) from the experimental data. Particularly in the continuous culture, wall growth was found to exert significant effects on the broth biomass concentration and phenol conversion, both of which decreased with increasing amounts of wall growth. These effects are opposite to those predicted by wall growth models and to experimental results of others using mixed culture (activated sludge) systems. 相似文献
18.
A flow cytometry analysis and in vitro enzyme activity study is carried out on the methylotrophic yeast, Hansenula polymorpha, during both (a) batch growth and (b) continuous cultures subjected to single perturbations in either system dilution rate or influent carbon substrate composition. Flow cytometry of yeasts growing diauxically on a glucose: methanol mixture during exponential growth, exhibit DNA and RNA distributions indicative of the S-synthesis-phase of the cell cycle. Cells at the stationary growth stage exhibit DNA and RNA distributions that indicate one portion of the population in the G
0/G 1 resting phase and another in the M-mitosis-phase.Yeast cells grown at a steady-state of D=0.2 h 1, then shifted to D=0.35 h –1, at a constant influent substrate mixture, are also examined with both flow cytometry and in vitro enzyme assays. Distributions of DNA, RNA, and total protein at either steady state and during the shift between dilution rates did not resemble any observed in batch culture. Flow cytometry indicates significant changes in cell composition within 20 min of the imposed dilution rate shift. In vitro enzyme assays show a response time in decreasing methanol oxidase activity of 2.5–3 h upon a dilution rate shift-up, while hexokinase activity increases to its steady-state level in less than 3 h. Similar cell compositional changes are reported for shifts in influent substrate methanol: glucose ratio at a constant dilution rate of D=0.35 h –1. Results suggest that an unsteady-state regime, oscillating between conditions that promote maximum enzyme activity of either glucose- or methanol-metabolizing enzymes, may allow simultaneous enhanced time-averaged production of both sets of enzymes. 相似文献
19.
Summary The steady-state concentration of M. trichosporium OB3b increased about two-fold in the continuous culture when the feeding medium was supplemented by ferrous sulphate (50mg/L) and citric acid (100mg/L) at a steady state. In batch and continuous cultures, the cell growth was significantly inhibited by excess N-sources (NH 4OH, NH 4Cl, NH 4NO 3, HNO 3, and NaNO 3) and ammonium N-sources were more inhibitory. Both volumetric O 2 transfer coefficient and specific O 2 uptake rate increased monotonously in an extensive range of air flow rate (0.1–7 vvm) and the methane interfered with the O 2 transfer even at very low flow rates (0.01–0.1 vvm). 相似文献
20.
The effect was studied of oxygen supply on the changes in total and specific rate of oxygen consumption by the cells, oxygen
transfer rate, saturation concentrations of dissolved oxygen and the yields of batch and continuous cultivations. Experiments
were done on the microorganism Klebsiella aerogenes CCM 2318 growing on synthetic glucose medium. Continuous cultivations were carried out at dilution rates of 0.96 and 0.178
h −1. The rate of oxygen transfer was determined by the sulphite method and the coefficient K La was assessed using the dynamic method with a correction for changes in the saturations of dissolved oxygen. A lowered oxygen
supply in batch cultivations caused deformations in the course of cell respiration. Comparison of results of batch and continuous
cultivations showed that the highest yields Y x/s and Y x/o are attained at low dilution rates without oxygen limitation. Batch cultivations, on the other hand, exhibit the lowest yields
and the highest cell respiration levels. In both types of cultivations, a respiration peak was ascertained under the conditions
of growth limitation by oxygen. 相似文献
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