Carbon dioxide evolution rate

Index Entries Pilot development unit scale dilute-acid hydrolysate fed-batch fermentation feed rate carbon dioxide evolution rate. 

Feed rate controlbased on the carbon dioxide evolution rate (CER) has been shown to be an efficient method. Taherzadeh et al. (14) increased the feed rate stepwise as long as the relative increase in CER was at least 50% of the relative increase in feed rate. Nilsson et al. (13) developed the method further and used the derivative of the CER to control the feed rate. This control principle was very successful in keeping the hexoses at low levels and preventing inhibition from toxic compounds and was the chosen control algorithm in the present work. 

By initializing the cell concentration, X(0), either from an estimation at some point of the oxygen uptake or carbon dioxide evolution rate or by knowing the inoculum size and then integrating the estimated growth rate over time, both cell biomass and growth rate can be estimated on-line utilizing a computer. The substrate (ethanol) demand, AS is then estimated by a similar equation, i.e. 

And, the carbon dioxide evolution rate (CER) provides a metabolic activity metric for aerobic and anaerobic fermentations ... 

Indirect measurement via computers appears to be a viable alternative to measurement involving sampling. Certain sensor information can be combined to give additional information such as oxygen-uptake rate, carbon-dioxide evolution rate, and respiratory quotient. These measurements can be thought of as gateway measurements because they make possible the calculation of additional information (Table 24.3). ... 

Time of fermentation (h) Carbon dioxide evolution rate (m Oxygen uptake rate (grti)... 

Ethylenediamine (15 g, 0 5 mol) was added dropwise to 100 ml 9B-100% formic acid in a two-necked 500 ml flask, fitted with an addition tube and reflux condenser with drying tube, cooled in an ice-bath. After complete addition of the base, 53 g of benzaldehyde (0.5 mol) was added in one lot. The ice-bath was removed and the flask was heated to the refluxing temperature. The initial rate of carbon dioxide evolution was too rapid to measure. After twenty minutes, the rate was circa 100 ml per minute and decreased rapidly to B ml per minute in one hour. Heating at reflux was continued for 35 hours. 

A full development of the rate law for the bimolecular reaction of MDI to yield carbodiimide and CO indicates that the reaction should truly be 2nd-order in MDI. This would be observed experimentally under conditions in which MDI is at limiting concentrations. This is not the case for these experimements MDI is present in considerable excess (usually 5.5-6 g of MDI (4.7-5.1 ml) are used in an 8.8 ml vessel). So at least at the early stages of reaction, the carbon dioxide evolution would be expected to display pseudo-zero order kinetics. As the amount of MDI is depleted, then 2nd-order kinetics should be observed. In fact, the asymptotic portion of the 225 C Isotherm can be fitted to a 2nd-order rate law. This kinetic analysis is consistent with a more detailed mechanism for the decomposition, in which 2 molecules of MDI form a cyclic intermediate through a thermally allowed [2+2] cycloaddition, which is formed at steady state concentrations and may then decompose to carbodiimide and carbon dioxide. Isocyanates and other related compounds have been reported to participate in [2 + 2] and [4 + 2] cycloaddition reactions (8.91. 

The acid-oxidant method is based on the idea that the hydrolysis of cellulose might be continuously determined from the rate of carbon dioxide evolution. Since, under controlled conditions, the rate of evolution of carbon dioxide is proportional to glucose concentration, it should be possible to follow the course of cellulose hydrolysis by means of the rate of carbon dioxide evolution provided that the sole final product of hydrolysis of cellulose is glucose. The latter assumption appears to be justified where the sample is reasonably pure. 

Todd reported that the respiration of pinto bean leaves was stimulated by exposure to ozone (at 4 ppm for 40 min). The first measurements were 4 h after the ozone exposure. The respiration rate later declined to the control value. In all cases, increased respiration correlated well with visible injury. MacdowalP confirmed these results, but made an additional observation during the first hour after ozone exposure (at 0.7 ppm for 1 h), and before visible symptoms appeared, respiration was inhibited. The increase in respiration took place only later, when visible symptoms appeared. Dugger and Palmer" reported an increase in respiration in lemon leaf tissue after 5 days of exposure to ozone at 0.15-0.25 ppm for 8 h/day. They reported no morphologic changes at that time. Anderson and Taylor S found that ozone induced carbon dioxide evolution in tobacco callus tissue. The threshold for evolution was about 0.1 ppm for 2 h in the sensitive Bel W,. The ozone concentration required for maximal carbon dioxide evolution was about twice as much in the more resistant cultivar. Formation of roots decreased sensitivity. 

The most fundamental work on polyethylene degradation is being done by A. C. Albertsson in Sweden(27,28,29,30,31) using elegant science with labelled polymers to measure the rate and quantity of carbon dioxide evolution from buried high and low density polyethylene films. Degradation occurs at about... 

In a 1-1. three-necked round-bottomed flask, wrapped with aluminum foil to exclude light, and equipped with a mechanical stirrer, a reflux condenser, and an addition funnel, is suspended 37 g. (0.17 mole) of red mercuric oxide (Note 1) in 330 ml. of carbon tetrachloride (Note 2). To the flask is added 30.0 g. (0.22 mole) of 3-chlorocyclobutaneearboxylic acid (Note 3), and the mixture is heated to reflux while stirring. To the mixture is added dropwise a solution of 40 g. (0.25 mole) of bromine in 180 ml. of carbon tetrachloride as fast as possible (4-7 minutes) without loss of bromine from the condenser (Note 4). After a short induction period, carbon dioxide is evolved at a rate of 150-200 bubbles per minute (Note 5). The solution is allowed to reflux until the rate of carbon dioxide evolution slows to about 5 bubbles per minute. This will usually take 25-30 minutes (Note 6). The mixture is then cooled in an ice bath, and the precipitate is removed by filtration. The residue on the funnel is washed with carbon tetrachloride, and the filtrates are combined. The solvent is removed by distillation using a modified Claisen distillation apparatus with a 6-cm. Vigreux column, and vacuum distillation of the residual oil gives 13-17 g. (35-46%) of... 

The effect of radiation on the biochemical processes of fresh fruits and vegetables is of considerable interest from the standpoint of its influence on shelf life. A number of studies on the effect of radiation on respiration have indicated a general stimulation of both oxygen uptake and carbon dioxide evolution during the irradiation period, subsiding to near-normal rates shortly following the cessation of treatment (21, 23, 24, 38). 

The ice-bath was removed and the flask was heated to the refluxing temperature. The initial rate of carbon dioxide evolution was too rapid to measure. After twenty minutes, the rate was circa 100 ml per minute and decreased rapidly to 8 ml per minute in one hour. Heating at reflux was continued for 35 hours. 

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