Power-time Curves Research Articles

The toxic effect on soil microbial activity caused by the free or immobilized pesticide diuron

The pesticide diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) was anchored onto silica gel to yield a new surface. Both free and immobilized pesticide were applied on typical Brazilian agricultural soil and the toxic effects on microbial activity of this red Latosol soil was followed by microcalorimetry. The activity of the microorganisms on 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose plus 6.0 mg of ammonium sulfate under 34.8% controlled humidity at 298.15±0.02 K. The activity was recorded through power–time curves for increasing amounts of the active principle, varying from 0 to 333.33 μg g −1. The increasing amounts of diuron, either free or immobilized, caused a decrease of the original thermal effect. The calorimetric data showed that the anchored pesticide presented a much lower toxic effect than free diuron on microbial activity.

Thermokinetic investigation of effect of temperature on optimum NaCl concentration for petroleum bacterial growth

The power–time curves of growth of three strains of petroleum bacteria at different NaCl concentrations at 40.0 and 50.0 °C have been determined by using a 2277 Thermometric Thermal Activity Analyser. An equation of a power–time curve, ln[ αP K / P( t)−1]=ln[( αK− N 0)/ N 0]− α kt, was established based on the generalized logistic equation, where P( t) is the thermal power at time t, K the carrying capacity, P K = P 0 K, P 0 the thermal power of one cell, N 0 the bacterial population at time zero, α=( k− D)/ k. The method of four observed points with the same time interval was used to calculate the value of P K . The growth rate constant k and the death rate constant D were calculated. The NaCl concentration of optimum growth rate of petroleum bacteria at 40.0 and 50.0 °C, respectively, have been obtained according to the curves k− D versus NaCl concentration, which are 0.26, 0.54 and 0.57 mol l −1 for B-1, B-2 and B-3, respectively, at 50.0 °C, 0.26, 0.55 and 0.56 mol l −1 for B-1, B-2 and B-3, respectively, at 40.0 °C. The results indicated that the effect of temperature on NaCl concentration of optimum growth rate was small.

Thermokinetic investigation of effects of carbon source on petroleum bacterial growth

The growth power–time curves of a strain of petroleum bacteria, B-2, in various kinds of cultures containing different kinds of carbon sources, glucose, n-tetradecane, n-hexadecane and n-octadecane, and different kinds of microemulsions have been determined by using a 2277 Thermal Activity Monitor. The curves showed a single peak for cultures containing a single carbon source, glucose, and two peaks for cultures containing two kinds of carbon sources, glucose and one of the n-alkanes. The first peak indicated that bacteria grew by consuming glucose and the second peak indicated that bacteria grew by consuming n-alkane. The curves were complex when the bacterium grows in a microemulsion culture. According to a kinetic equation of bacterial growth under limited conditions, the rate constants of bacterial growth were obtained. The results showed that the microemulsion culture was more appropriate to bacteria to grow on n-alkanes.

Microcalorimetric Study of the Oscillating Extraction System

The power–time curves of the oscillating extraction system were determined at different temperatures for the extraction of hydrochloric acid and acetic acid with primary amine N1923 (R–CH(NH2)–R1), R, R1 represent alkyl of C9–11 in chloroform using the titration microcalorimetric method. The apparent activation energy was calculated from the induction period (tin), the first oscillation period (tp.1) and the second oscillation period (tp.2).

Thermokinetics of Activation of Metal Ions to Amylase Catalyzed Reaction

Power-time curves ofamylase catalyzed reaction with or without activation were obtained with a 2277thermal activity monitor(Sweden). The data of Km and vmax were calculated for enzyme catalyzed reactions without activation. Data of apparent and vmax were calculated for activation (Ca2+, Mg2+) using thermoki IMG SRC="IMAGE/01220553.JPG" HEIGHT=11 WIDTH=12netics theory and reduced extent method. From the relationship between and concentration of metal ions(c), theeffects of the activation were gained for metal ions of amylase catalyzed reaction.

A microcalorimetric study of the biologic effect of Mn(II) on Bacillus thuringiensis growth

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the effect of Mn(II) on Bacillus thuringiensis. The power-time curves of the growth metabolism of B. thuringiensis and the effect of Mn(II) on it were studied using an LKB-2277 BioActivity Monitor, ampoules method, at 28°C. For evaluation of the results, the maximum peak-heat output power (P max) in the growth phase, the growth rate constants (k), the log phase heat effects (Q log ), and the total heat effect in 23 h (Q T) for B. thuringiensis were determined. Manganese has been regarded as the essential biological trace element. Mn(II) of different concentration have different effects on B. thuringiensis growth metabolism. High concentration (800-1600 μg mL-1) of Mn(II) can promote the growth of B. thuringiensis; low concentration (500-800 μg mL-1) can inhabit its growth.

Microcalorimetric study of the action of Ce(III) ions on the growth of E. coli.

A microcalorimetric technique based on bacterial heat output was used to evaluate the action of Ce(III) ions on the growth of Escherichia coli. The power-time curves of the growth metabolism of the bacteria were studied in the presence and absence of Ce(III) by means of a LKB-2277 Bioactivity Monitor, by a stopped-flow method at 37 degrees C. For evaluation of the results, the maximum power, Pmax, the growth rate constant k, and the heat effects Qlog, Qstat, and Qtot for the log phase, the stationary phase, and total heat output, respectively, were determined. For comparison, a spectrophotometer was used to estimate the number of cells in the liquid culture. The shape of the bacteria was examined by electron microscopy. We concluded that the presence of cerium ions at concentrations below 350 microg/mL have a stimulatory effect on the growth of E. coli, whereas concentrations at or above 400 microg/mL may have an inhibitory effect.

Microcalorimetric study of the metabolism of U-937 cells undergoing apoptosis induced by the combined treatment of hyperthermia and chemotherapy

Hyperthermia is a useful adjunct in cancer therapy, as it can increase the effectiveness and decrease the toxicity of currently available cancer treatments such as chemotherapy and radiation. In this study we determined the power-time curves of U-937 cell line treated by the combination of hyperthermia and Carmofur by using an LKB 2277 Bioactivity Monitor. The maximal thermal power and the heat production were used to evaluate the antitumor effect. Our results show that the combined treatment of hyperthermia and Carmofur had a synergistic antitumor effect, which is consistent with the apoptosis ratio obtained by TUNEL assay. The results also indicate that the metabolic activity of apoptotic cells is lower than that of normal cells. Thus microcalorimetry is a powerful tool in fields of hyperthermia.

THERMOCHEMISTRY STUDY ON THE EXTRACTION OF Co(II) AND Ni(II) WITH CYANEX 272 IN KEROSENE1*

The extraction of Co(II) and Ni(II) from sulfate solution with Cyanex 272 in kerosene has been studied by titration microcalorimetry. The heats produced in the reaction processes were determined by the power–time curves and the ΔrHθ m values at 298 K were identified. The extraction equilibrium constants and thermodynamic functions at different temperatures were calculated. *This study is supported by the National Natural Science Foundation of China (29971020) and the Natural Science Foundation of Shandong Province (L2000B01).

The effect of the herbicide diuron on soil microbial activity.

The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.

Study of Thermokinetic Properties of Sodium Selenite on Bacillus thuringiensis Cry B by Microcalorimetry

AbstractBy using an LKB2277 Bioactivity Monitor, the power‐time curves of Bacillus thuringiensis Cry B at 28°C effected by Na2SeO3 were determined. Some parameters, such as growth rate constants k, inhibitory ratio I, the maximum beat production rate Pmax, heat output Q, were obtained. Considering both the growth rate constant k and heat output Q, we found that a low concentration of Na2SeO3 had a promoting action on the growth of Bacillus thuringiensis Cry B, but a high concentration of Na2SeO3 had an inhibitory action. The toxicity of a toxicant can also be expressed as half inhibitory concentration IC50 of toxicant, i. e., 50% effective in this inhibition. The value of IC50 of Na2SeO3on Bacillus thuringiensis Cry B is 117 μg/mL. This microcalorimetric bioassay for cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile.

Thermodynamic studies on the effects of cisplatin or its analog complexes on actin polymerization

The effects of cisplatin or its analog complexes on actin polymerization have been studied by the microcalorimetric and viscosity methods at the temperature of 310.15 K. The thermodynamic parameters and the power–time curves of actin polymerization in the presence of cisplatin or its analog complexes ( cis-DBDP, cis-DIDP, cis-DADP) are measured. The results show that there are different interaction mechanisms between actin and cisplatin or its analog complexes. The relative viscosity of actin polymer decreases in the presence of cisplatin or its analogs, and also shows Pt concentration dependence. It indicates that these compounds affect actin polymerization. It has been discussed from the experimental results that the presence of cisplatin or its analog complexes cause different polymerization mechanism of actin.

Microcalorimetry of the degradation of the herbicide 2,4-D via the microbial population on a typical Brazilian red Latosol soil

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was applied to a typical Brazilian red Latosol soil. The thermal effects evolved by 2,4-D degradation were followed in a series of microcalorimetric experiments. The power–time curves were recorded for increasing doses of herbicide, varying from 0 to 6.67mgg−1 under a 34.8% controlled humidity. The herbicide was used as a food source by soil microbes, the degradation causing the thermal effect. The thermal effect increases to 2.67mgg−1. Above this concentration, a decrease of the thermal effect was observed due to toxicity of 2,4-D to the microbes.

THERMO-KINETIC INVESTIGATION OF OPTIMUM GROWTH TEMPERATURE OF PETROLEUM BACTERIA

The power-time curves of the growth of three strains of petroleum bacteria at different temperatures have been determined. A novel equation of a power-time curve has been proposed in this paper. The general formula to calculate the rate constant of the bacterial growth has been derived. The rate constants of the bacterial growth at different temperatures, the heat production per newly formed bacterium, the bacterial number at the end of the bacterial growth and the deceleration rate constant of the bacterial growth at 50.00°C, have been calculated. The optimum growth temperatures of the three strains have been obtained.

MICROCALORIMETRIC MONITORING OF ANAEROBIC DIGESTION PROCESSES

Microcalorimetry was used for monitoring anaerobic digestion processes of heavily polluted industrial waste waters (from cheese industry, distilleries, yeast plant). Interpreting the thermal power-time curves by HPLC, some sub-processes in batch cultures were tentatively identified as acidogenic, acetogenic and methanogenic. Processes underlying power-time curves up to 10 h were different for different wastes. In the case of cheese whey and distillery waste it was acidogenesis, in the case of sulfate containing waste - presumably reduction of sulfates. The effect of Biotreat 100 (BimKemi Eesti Ltd.), a preparation for removing H2S from waste water, was observed for these processes.

STUDY OF A BIOLOGICAL OSCILLATION SYSTEM BY A MICROCALORIMETRIC METHOD

The power–time curves of a biological oscillation system were determined for different temperatures, acidities and carbon sources, by using a 2277 thermal activity monitor. The apparent activation energy and order of the oscillation reaction were calculated from the induction period (tin) and the first oscillation period (tp). The regularity of the biological oscillation system is discussed.

Toxic effect caused on microflora of soil by pesticide picloram application.

The toxic effect of the herbicide picloram on the microbial population of a typical Brazilian red Latosol soil was studied in a series of microcalorimetric experiments. The activity of the soil was stimulated by the addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate, under 34.8% controlled moisture, to a 1.50 mg soil sample, at 298.15 +/- 0.02 K. The net thermal effect due to the addition of the picloram to the soil was determined by interpreting the power-time curves, which were recorded on the microcalorimeter. The total thermal effect evolved by the microorganisms was affected by the increasing doses of herbicide, and varied from 0 to 10.00 micrograms g-1. An increase in picloram exposure caused a decrease of the original thermal effect, reaching a null value above 20.89 micrograms of herbicide per gram of soil. The decreases of the thermal effect evolved by microorganisms and the increase of the lag phase period are associated with the death of the microbial population. The effects caused by picloram application in this typical Brazilian soil resulted in a strong effect on the soil microbial communities.

A microcalorimetric method for studying the biological effects of La 3+ on Escherichia coli

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the stimulatory effect of La 3+ on Escherichia coli. The power–time curves of the growth metabolism of E. coli and the effect of La 3+ on it were studied using an LKB-2277 BioActivity Monitor, stopped-flow method, at 37°C. For evaluation of the results, the maximum power ( P max), the growth rate constants ( k) and the heat effects ( Q LOG, Q STAT) for the log phase, the stationary phase and the total heat effect ( Q T) for E. coli were determined. The microcalorimetric method agreed with the conventional methods, such as cell numbers and biomass. La 3+ in the concentration ranges of 0–400 μg/ml has stimulatory effects on E. coli, while La 3+ ion of higher concentrations (>400 μg/ml) can inhibit the growth. This phenomenon is very similar to those observed from the in vitro cells and tissues from animals, plants and some microorganisms by other methods.

The effects of environmental conditions on the growth of petroleum microbes by microcalorimetry

The growth and metabolism ability of two strains of petroleum microbe isolated from oil reservoirs was studied by calorimetry. Thermal power–time curves under various environmental conditions (including temperature, acidity, salinity and carbon source) were determined. Typical microbial growth thermal power–time curves were obtained. By fitting the curves mathematically with the ‘three-point method’ under an inhibitory condition, the growth rate constants and the optimum growth conditions (including temperature, acidity and salinity) of the microbes studied were obtained. Irregular thermal power–time curves were obtained when the petroleum microbe E grew in the media containing different carbon sources.

Effect of the pesticide 2,4-D on microbial activity of the soil monitored by microcalorimetry

Microcalorimetry was applied in a series of experiments to follow the effect caused by the pesticide 2,4-dichlorophenoxiacetic acid (2,4-D) on microbial activity of red Latosol soil. The activity of the soil was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under a 35% controlled humidity in a soil sample of 1.50 mg. Power–time curves recorded on calorimeter were followed by the increasing amount of the pesticide, from 0 to 10.0 mg, which affected directly the total thermal effect evolved by microorganisms. The curves showed a synergism on total thermal effect obtained by addition of 1.0 mg of pesticide, causing a consumption of 2,4-D by microorganisms, as a new source of nutrients. However, above this mass, the total thermal effect decreased exponentially. The increase of the amount of pesticide is associated to a decrease on the microbial activity of the soil, probable due to the increase of the toxic products formed from degraded 2,4-D, affecting strongly the life in this ecosystem.