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At least 199 records · Page 11Linked to original sources

PubMed2000

Effect of feeding strategy on Zymomonas mobilis CP4 fed-batch fermentations and mathematical modeling of the system.

In this work, the effect of the feeding strategy in Zymomonas mobilis CP4 fed-batch fermentations on the final biomass and ethanol concentrations was studied. Highest glucose yields to biomass (0.018 g/g) and to ethanol (0.188 g/g) were obtained in fed-batch fermentations carried out using different feeding rates with a glucose concentration in the feed equal to 100 g/l. Lower values (0.0102 g biomass/g glucose and 0.085 g ethanol/ g glucose) were obtained when glucose accumulated to levels higher than 60 g/l. On the other hand, the highest biomass (5 g/l) and ethanol (39 g/l) concentrations were obtained using a glucose concentration in the feed equal to 220 g/l and exponentially varied feeding rates. Experimental data were used to validate the mathematical model of the system. The prediction errors of the model are 0.39, 14.36 and 3.24 g/l for the biomass, glucose and ethanol concentrations, respectively. Due to the complex relationship for describing the specific growth rate, a fed-batch culture in which glucose concentration is constant would not optimize the process.

Ethanol↗

PubMed2003

The effect of growth phase on the lipid class, fatty acid and sterol composition in the marine dinoflagellate, Gymnodinium sp. in batch culture.

We have studied the effects of growth phase on the lipid composition in batch cultures of Gymnodinium sp. CS-380/3 over 43 days of culturing. The lipid content increased two fold, from late logarithmic (day 6) to linear growth phase (day 22) then decreased at stationary phase (day 43) while the lipid yield (mg l(-1)) increased 30-fold from day 6 to 30 mg l(-1) at day 43. Changes in fatty acid content mirrored those observed for the total lipid, while the sterol content continued to increase with culture age through to stationary phase. The largest changes occurred in the lipid classes, especially the polar lipids and triacylglycerols (oil). The proportion of triacylglycerols increased from 8% (of total lipids) at day 6 to 30% at day 43, with a concomitant decrease in the polar lipid fraction. The proportions of 16:0 and DHA [22:6(n-3)] increased while those of 18:5(n-3) and EPA [20:5(n-3)] decreased with increasing culture age. The proportion of the major sterol, dinosterol, decreased from 41% (day 6) to 29% (day 43), while the major dinostanol epimer (23R,24R) increased from 33% (day 6) to 38% (day 22). Despite small changes in the proportion of the main sterols, the same sterols were present at all stages of growth, indicating their value as a chemotaxonomic tool for distinguishing between strains within the same genus. Growth phase could be a useful variable for optimising the oil and DHA content with potential for aquaculture feeds and a source of DHA-rich oils for nutraceuticals.

Animals↗

PubMed2006

Equilibrium and thermodynamic parameters of single and binary mixture biosorption of lead (II) and copper (II) ions onto Pseudomonas putida: effect of temperature.

The biosorption of lead (II) and copper (II) ions, single component and binary systems, by dried P. putida was investigated in a batch system. The effects of initial pH, temperature, initial single and binary mixture concentrations on the biosorption kinetics and equilibrium uptake of each component, both single and binary mixtures were investigated. The bacterial biomass exhibited the highest single and binary lead (II) and copper (II) ions uptake capacity at 25 and 30 degrees C, respectively, the initial pH value of 5.5 and at the initial metal ions concentration of 100 mg dm(-3). The Freundlich and Langmuir adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants were evaluated at different temperatures. Adsorption data were well described by the Langmuir model, although they could be modeled by the Freundlich equation. The thermodynamics constants of the adsorption process: DeltaH degrees , DeltaS degrees and DeltaG degrees were evaluated. The results showed that biosorption of single and binary lead (II) ions on P. putida were exothermic and spontaneous. While biosorption of single and binary copper (II) ions on P. putida was endothermic and spontaneous.

Adsorption↗

PubMedDate not supplied

Fed-batch cultivation of Saccharomyces cerevisiae in a hyperbaric bioreactor.

Fed-batch is the dominating mode of operation in high-cell-density cultures of Saccharomyces cerevisae in processes such as the production of baker's yeast and recombinant proteins, where the high oxygen demand of these cultures makes its supply an important and difficult task. The aim of this work was to study the use of hyperbaric air for oxygen mass transfer improvement on S. cerevisiae fed-batch cultivation. The effects of increased air pressure up to 1.5 MPa on cell behavior were investigated. The effects of oxygen and carbon dioxide were dissociated from the effects of total pressure by the use of pure oxygen and gas mixtures enriched with CO(2). Fed-batch experiments were performed in a stirred tank reactor with a 600 mL stainless steel vessel. An exponential feeding profile at dilution rates up to 0.1 h(-)(1) was used in order to ensure a subcritical flux of substrate and, consequently, to prevent ethanol formation due to glucose excess. The ethanol production observed at atmospheric pressure was reduced by the bioreactor pressurization up to 1.0 MPa. The maximum biomass yield, 0.5 g g(-)(1) (cell mass produced per mass of glucose consumed) was attained whenever pressure was increased gradually through time. This demonstrates the adaptive behavior of the cells to the hyperbaric conditions. This work proved that hyperbaric air up to 1.0 MPa (0.2 MPa of oxygen partial pressure) could be applied to S. cerevisiae cultivation under low glucose flux. Above that critical oxygen partial pressure value, i.e., for oxygen pressures of 0.32 and 0.5 MPa, a drastic cell growth inhibition and viability loss were observed. The increase of carbon dioxide partial pressure in the gas mixture up to 48 kPa slightly decreased the overall cell mass yield but had negligible effects on cell viability.

Adaptation, Physiological↗

PubMed2003

Am(III) adsorption on oxides of aluminium and silicon: effects of humic substances, pH, and ionic strength.

The adsorption of Am(III) (total concentration 10(-9) mol/l) on alumina, silica, and hematite was studied by a batch technique. The effects of pH, ionic strength, and humic substances on the adsorption of Am(III) on alumina and silica were investigated, and the adsorption isotherms of Am(III) on alumina and silica at different pH values were determined. It was found that compared with the adsorption of Am(III) on alumina, the adsorbability of silica on the basis of mass is less, the relative adsorption rate on silica is slower, the sensitivity of adsorption on silica to ionic strength is less, the dependence of adsorption on silica on pH is gentler, and consequently that the adsorption characteristics of Am(III) on alumina and silica are distinctly different. The negative effect of fulvic acid on the adsorption on silica and the positive effect of humic acid on the adsorption on alumina were found. In contrast to the Am(III) adsorption on alumina and silica, a tremendously high adsorbability of Am(III) on hematite was found. The sequence of adsorbabilities of Am(III) on the basis of mass is Fe2O3 > Al2O3 > SiO2.

Journal Article↗

PubMed2005

Continuous hydrogen production from organic waste.

The antibiotic effects of lactic acid bacteria, Lactobacillus paracasei, on hydrogen production were investigated using glucose as the substrate for the batch experiments. The effects of lactic acid bacteria on hydrogen fermentation depended on pH and the inhibition of hydrogen-producing bacteria was prevented by keeping the pH over 5.0. Then, a continuous hydrogen production experiment was conducted by using bean curd manufacturing waste as an actual organic waste at pH 5.5 at 35 degrees C. The increase of the substrate concentration and the addition of nitrogen gave precedence to acetic and butyric acids production in the metabolic pathway and suppressed propionic acid production. As the result, continuous hydrogen production from municipal organic waste was enabled.

Ammonium Chloride↗

PubMed1986

[Stimulation of Brucella clearance in rats after treatment with BCG suspensions].

Intraperitoneal application of BCG induced a significantly increased clearance of Brucella in rats. The effect starts three days after application of 7 mg BCG to the rat and continued for eight weeks. This effect could be used for estimation of efficiency of BCG for nonspecific resistance stimulation. Comparative investigation of seven different batches reveals that three BCG preparations induce an unspecific resistance more than eight weeks, one for two weeks and three batches exerted no effect. Addition of Gelafusal as a stabilizer prolonged durability for about two weeks.

Animals↗

PubMed2003

Biophotonic patterns of optical interactions between fish eggs and embryos.

The optical (non-substantial) interactions between various biological samples have been evident in a number of cases mainly by the effects on their functional activity and developmental patterns. However, the mechanisms of these interactions have remained obscure. Effect of optical interaction has been observed on the intensity and Fourier patterns of biophoton emission of fish embryos. We demonstrate that: (1) the short-term optical interactions are accompanied by a gradual decrease of a total emission intensity of the interacting batches; (2) this effect is spread laterally to that part of a batch which does not have any direct optical contacts with its partner; and (3) the long-term optical contacts lead to a mutual exchange of spectral characteristics of interacting batches in which the total spectral density values are reversed (often with an overshoot). The reversal rate depends upon the developmental distance between the optical partners and the initial differences of their spectral characteristics. The results are discussed in terms of a sub-radiance and Le Chatelier principle.

Animals↗

PubMed1988

Retention reproducibility of basic drugs in high-performance liquid chromatography on a silica column with a methanol-ammonium nitrate eluent. Batch-to-batch reproducibility of the stationary phase.

The effect of changing the brand and batches of the silica stationary phase used with a methanol-aqueous ammonium nitrate eluent for the high-performance liquid chromatographic separation of basic drugs has been studied. Considerable care had to be taken to obtain a reproducible eluent and the effect of small changes in the concentration of the ammonia solution were examined closely. Large differences in both the capacity factor and relative capacity factors were found for separations on columns packed with four different brands of silica. Significant differences were also observed with columns containing eighteen different batches of Spherisorb S5W, which had been manufactured over a period of several years.

Chromatography, High Pressure Liquid↗

PubMed2006

Ammonia removal from leachate solution using natural Chinese clinoptilolite.

This paper assesses the potential of natural Chinese clinoptilolite for ammonia removal from the leachate solution of sewage sludge. In batch study the effects of relevant parameters, such as contact time, initial ammonia concentration and particle size of clinoptilolite, were examined respectively. The results show that the data obtained from batch studies were fit to Langmuir and Freundlich isotherms and the Langmuir isotherms reflect more reasonable for ammonium ion uptake onto clinoptilolite; the clinoptilolite adsorption process has been proved effective, at laboratory scale, the maximum adsorption capacity of the clinoptilolite, for ammonium concentration ranging from 11.12 to 115.16 mg NH(4)-N L(-1) in leachate solution, was about 1.74 mg NH(4)-Ng(-1); the time to adsorption equilibrium was 2.5 h in leachate solution and 1.5 h more than for in NH(4)Cl synthetic solution; ammonium adsorption increased with decreasing clinoptilolite particle size; the ammonia removal capacity of clinoptilolite increased with increasing initial ammonia concentration. It is believed that as adsorption agent for NH(4)-N removal from sludge leachate, natural Chinese clinoptilolite can be feasible.

Adsorption↗

PubMed2005

The effect of temperature and sludge age on COD removal and nitrification in a moving bed sequencing batch biofilm reactor.

This study investigates the effect of temperature and the sludge age on the performance of a moving bed sequencing batch biofilm reactor (MBSBBR) for COD removal and nitrification. The experiments are conducted in a lab-scale MBSBBR operated at three different temperatures (20, 15 and 10 degrees C) with a synthetic feed simulating domestic sewage characteristics. Evaluation of the results revealed that removal of organic matter at high rates and with efficiencies over 90% was secured at all operation conditions applied. The nitrification rate was significantly influenced by changes in temperature but complete nitrification occurred at each temperature. The nitrification rates observed at 20 and 15 degrees C were very close (0.241 mg NO(x)-N/m2d, 0.252 mg NO(x)-N/m2 d, respectively), but at 10 degrees C, it decreased to 0.178 mg NO(x)-N/m2d. On the other hand, the biomass concentration and sludge age increased while the VSS/TSS ratios that can be accepted as an indicator of active biomass fraction decreased with time. It is considered that, increasing biofilm thickness and diffusion limitation affected the treatment efficiency, especially nitrification rate, negatively.

Biofilms↗

PubMed2004

Mechanochemical removal of organo-chlorinated compounds by inorganic components of soil.

The purpose of this work is to evaluate the catalytic efficiency of two metal oxides, ferrihydrite and birnessite and of a ferruginous smectite, towards organic molecules such as 4-chloroaniline (4-CA), pentachlorophenol (PCP), and five polychlorinated biphenyls (PCBs) characterised by different number and position of chlorine atoms. Mechanochemical dry contacts with light grinding between catalytic surfaces and pollutants have been carried out. The efficiency of the mechanochemical removal was compared with batch experiments for the soluble compounds (PCP and 4-CA). The removal of 4-CA and PCP by the mechanochemical procedure resulted more effective than by batch contact in the presence of birnessite and ferrihydrite, particularly at higher pH (100% removal of 4-CA by birnessite in 30 min at pH 8.6 after the mechanochemical contact compared to 20% removal using the batch interaction at the same pH). The mechanochemical contact of PCBs and birnessite produced a removal of pollutant that was a function of the number of chlorine atoms (complete removal of 2,2'-dichlorobiphenyl in 10 days and a removal of 30% and 20% of 2',3,4-trichlorobiphenyl and 3,3',4,4'-tetrachlorobiphenyl, respectively in 90 days) and of the position of chlorine atoms about the biphenyl rings (100% of 2,2'-dichlorobiphenyl in 10 days, 84% of 3,3'-dichlorobiphenyl in 15 days and 40% of 4,4'-dichlorobiphenyl in 27 days).

Aniline Compounds↗

PubMed1986

Comparison of antibody levels and protective efficacy against pneumococci in two immunoglobulin preparations for intravenous use.

Passive immunization with modern intravenous immunoglobulin preparations might be used prophylactically in individuals at extreme risk of contracting postsplenectomy sepsis or therapeutically in established infections. Since pneumococci are the predominant causative organisms, we determined antibodies against 14 pneumococcal serotypes in two commercially available immunoglobulin preparations (two batches of each) using enzyme-linked immunosorbent assay. The four batches were remarkably similar in antibody content. Low levels against some clinically important serotypes, i.e. types 3, 8 and 18C were recorded. The protective effect of one batch of each preparation against type 1 pneumococci was documented in splenectomized rats.

Animals↗

PubMed1985

Time and cost comparison of four methods of filling drug manufacturers' piggyback bottles.

The times and costs required for four methods of reconstituting i.v. antibiotic doses in drug manufacturers' piggyback bottles (DMPBs) were compared. Instafil filling devices were used with (1) a pressure cuff (Instafil Instafusor) for the diluent bag, (2) a peristaltic pump (Wheaton Unispense), and (3) a vacuum line. The fourth method used a vacuum line and a control handle (Vacu-fil, American McGaw). Batches of 20 bottles filled to 50 mL and 20 bottles filled to 100 mL (three trials each) and 60 bottles filled to 100 mL (two trials) were prepared by each of the four methods. The Instafil with vacuum line was significantly faster than the other methods used to fill batches of 20 DMPBs with 50 mL and 100 mL of diluent. It was also significantly faster than the Vacu-fil and the Instafil with the cuff for filling batches of 60 DMPBs with 100 mL of diluent. For batches of 60 DMPBs, the fill times for the Instafil with vacuum line and the Instafil with the peristaltic pump were not significantly different. For the batches of 20 50-mL DMPBs, overall cost per dose for the Instafil with vacuum line was $0.36, followed by Instafil with the pump ($0.37), Instafil with cuff ($0.38), and Vacu-fil ($0.54). Other batch sizes and fill volumes ranked similarly. Of the methods tested, the Instafil device with a vacuum line was the most efficient and cost-effective for preparing batches of 20 to 60 i.v. antibiotic doses in manufacturers' piggyback bottles.

Boston↗

PubMed1989

The influence of growth phase and culture conditions of Tetrahymena on effects of cadmium.

The batch culture system is used in the majority of toxicity studies employing protozoa and other cell cultures, although it is known that metal toxicity may vary depending on the age and therefore on the physiological state of the culture. The ciliate Tetrahymena was exposed to cadmium during short-term incubations at different stages of the growth cycle. In cultures with cells proliferating at a high rate (log phase cells) the toxicity of cadmium was found to increase with increasing initial cell density. However, in the subsequent stationary growth phase with decreased rate of cell proliferation, the sensitivity against cadmium again decreases. Thus the effect of a given concentration of cadmium depends on the initial cell density of the culture. This effect of cadmium may be explained either by changes in the chemical composition of the culture medium during the growth cycle or by a changed cellular metabolism. Furthermore, it is shown that the cadmium concentration of the medium decreases during prolonged exposure when the cells are grown in batch cultures. Some of the problems associated with the toxicity bioassay performed in a static system may be overcome by using a continuous flow system. In such a system, Tetrahymena can be kept under optimal growth conditions with a generation time of less than 3 h, and any cell density may be maintained for extended periods of time. Furthermore, the cadmium concentration of the medium remained constant during prolonged exposure when maintaining a cell density of about 50 x 10(3) cells/ml. This illustrates the great advantage of using a continuous flow system in such investigations, where for example, long-term adaptations of the organism to a metal may be studied under constant conditions.

Animals↗

PubMed2001

Degradation of cyanobacterial hepatotoxins in batch experiments.

Bank filtration offers a cost effective and low maintenance technique for the removal of cyanobacterial hepatotoxins from drinking water. For bank filtration to be effective, the toxins must be degraded. The broad aim of this research was to determine whether the hepatotoxins, nodularin and microcystin-LR, could be completely removed from the soil/water matrix of three soils by microbial degradation. The results indicated that complete toxin removal was possible within 10-16 d in 2/3 soils that were incubated in the dark at 20 degrees C. The soils with the highest organic carbon content (2.9%) and the highest clay content (16.1%) were the most effective at removing the toxins in batch experiments. However, the sandy soil (98.5% sand) was incapable of degrading either toxin. The half-lives of toxin losses due to adsorption, desorption and degradation were calculated and for all soils. The degradation process had the highest half-life for both toxins. This suggested that degradation was likely to be the rate-limiting step of complete toxin removal. It was concluded that when a bank filtration site was being chosen, the degradation potential and the textural properties of the riverbank soil would be important when considering complete removal of cyanobacterial hepatotoxins.

Adsorption↗

PubMed2004

Photocatalytic degradation of model textile dyes in wastewater using ZnO as semiconductor catalyst.

Semiconductor photocatalysis often leads to partial or complete mineralization of organic pollutants. Upon irradiation with UV/visible light, semiconductors catalyze redox reactions in presence of air/O2 and water. Here, the potential of a common semiconductor, ZnO, has been explored as an effective catalyst for the photodegradation of two model dyes: Methylene Blue and Eosin Y. A 16 W lamp was the source of UV-radiation in a batch reactor. The effects of process parameters like, catalyst loading, initial dye concentration, airflow rate, UV-radiation intensity, and pH on the extent of photo degradation have been investigated. Substantial reduction of COD, besides removal of colour, was also achieved. A rate equation for the degradation based on Langmuir-Hinshelwood model has been proposed.

Catalysis↗

PubMed1998

Aerobic microbial degradation of aromatic sulfur-containing compounds and effect of chemical structures.

Batch data of aerobic microbial degradation rate constants Kb of phenylthio, phenylsulfinyl and phenylsulfonyl acetates have been determined, and the qualitative relationships between their Kb and chemical structures were analyzed. The phenylthio acetates were most subject to microbial transformation, followed by the phenylsulfonyl acetates. The compounds with a methoxy group were easier degraded than those with a isopropoxy group. The nitro-group and chloro-group on benzene were shown to lower the biodegradability, while the nitro-group at the para-position had stronger side effect on degradation than at the ortho-position.

Benzene Derivatives↗