The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform

J. J. Heijnen - One of the best experts on this subject based on the ideXlab platform.

  • Determination of in vivo oxygen uptake and Carbon Dioxide Evolution rates from off-gas measurements under highly dynamic conditions.
    Biotechnology and bioengineering, 2002
    Co-Authors: H. C. Lange, W.m. Van Gulik, J. J. Heijnen
    Abstract:

    In vivo kinetics of Saccharomyces cerevisiae are studied, in a time window of 150 s, by analyzing the response of O2 and CO2 in the fermentor off-gas after perturbation of chemostat cultures by metabolite pulses. Here, a new mathematical method is presented for the estimation of the in vivo oxygen uptake rate (OUR) and Carbon Dioxide Evolution rate (CER) directly from the off-gas data in such perturbation experiments. The mathematical construction allows effective elimination of delay and distortion in the off-gas measurement signal under highly dynamic conditions. A black box model for the fermentor off-gas system is first obtained by system identification, followed by the construction of an optimal linear filter, based on the identified off-gas model. The method is applied to glucose and ethanol pulses performed on chemostat cultures of S. cerevisiae. The estimated OUR is shown to be consistent with the independent dissolved oxygen measurement. The estimated in vivo OUR and CER provide valuable insights into the complex dynamic behavior of yeast and are essential for the establishment and validation of in vivo kinetic models of primary metabolism. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 81: 448–458, 2003.

  • Modeling and experimental validation of Carbon Dioxide Evolution in alkalophilic cultures.
    Biotechnology and bioengineering, 1992
    Co-Authors: H. J. Noorman, G. C. A. Luijkx, K. Ch. A. M. Luyben, J. J. Heijnen
    Abstract:

    The chemical reactions involving Carbon Dioxide in mineral culture media are considered. A mathematic model is set up, based on published data, which is valid at pH values below 9, and in which the nonideality of the solution is taken into account. The crucial parameter is the constant expressing the equilibrium between Carbon Dioxide and biCarbonate, K1. The reactions were studied in three different aqueous solutions: water, mineral salt medium, and a suspension with nongrowing bacterial cells. For each situation, three methods were compared for the determination of the biCarbonate concentration in the solution: equilibrium state total Carbon analysis, dynamic monitoring of the rate of acid or alkali addition, and dynamic measurement of the Carbon Dioxide gas phase mole fraction. In a batch-stirred tank reactor, the equilibrium constant K1 agreed with the published value, and the three biCarbonate analysis methods give the same results. If the nonideality is not taken into account, the result significantly differed from the published value and is likely to be incorrect. A real alkalophilic process, using Acinetobacter calcoaceticus in a continuous stirred tank reactor at steady state, also gave results that are in accord with the literature. However, the results do not allow validation of the equation expressing the nonideality. The steady state in the batch system and in continuous culture can be well described with the mathematical model. However, in the transient state there are some unexplained differences between simulation and measurement.

Håkan Jönsson - One of the best experts on this subject based on the ideXlab platform.

  • Process inhibition due to organic acids in fed-batch composting of food waste – influence of starting culture
    Biodegradation, 2005
    Co-Authors: Cecilia Sundberg, Håkan Jönsson
    Abstract:

    Inhibition of the degradation during low pH conditions has been observed in fed-batch composting systems. To analyse this phenomenon, fed-batch composting of food waste with different amounts of starting culture was examined in laboratory reactor experiments. Changes in temperature, Carbon Dioxide Evolution, pH, solids, ash and short chain organic acids were measured. In reactors with a daily feed rate of 24% or less of the starting culture, thermophilic temperatures occurred and the pH and Carbon Dioxide Evolution were high and stable after a starting period of 4–5 days. In reactors with a daily feed rate of 48% or more of the starting culture the composting process failed, as the pH dropped below 6 and remained there and the temperature and Carbon Dioxide Evolution were low. It was concluded that the use of adequate amounts of starting culture consisting of active compost can efficiently prevent low pH conditions and process inhibition in fed-batch composting of food waste.

  • Process inhibition due to organic acids in fed-batch composting of food waste--influence of starting culture.
    Biodegradation, 2005
    Co-Authors: Cecilia Sundberg, Håkan Jönsson
    Abstract:

    Inhibition of the degradation during low pH conditions has been observed in fed-batch composting systems. To analyse this phenomenon, fed-batch composting of food waste with different amounts of starting culture was examined in laboratory reactor experiments. Changes in temperature, Carbon Dioxide Evolution, pH, solids, ash and short chain organic acids were measured. In reactors with a daily feed rate of 24% or less of the starting culture, thermophilic temperatures occurred and the pH and Carbon Dioxide Evolution were high and stable after a starting period of 4-5 days. In reactors with a daily feed rate of 48% or more of the starting culture the composting process failed, as the pH dropped below 6 and remained there and the temperature and Carbon Dioxide Evolution were low. It was concluded that the use of adequate amounts of starting culture consisting of active compost can efficiently prevent low pH conditions and process inhibition in fed-batch composting of food waste.

Manjit K. Misra - One of the best experts on this subject based on the ideXlab platform.

  • Carbon Dioxide Evolution FROM FRESH AND PRESERVED SOYBEANS
    Transactions of the ASAE, 2004
    Co-Authors: Ibni Hajar Rukunudin, Carl J. Bern, Manjit K. Misra, Theodore B. Bailey
    Abstract:

    Carbon Dioxide Evolution has proven to be a good indicator of deterioration in studies of stored cereal grains and oilseeds. Since little work has been done with stored soybeans, a study was conducted measuring Carbon Dioxide from stored soybeans using freshly harvested and preserved soybean samples. The objective of the study was to determine the effects of harvesting method, storage temperature, storage moisture content, and storage time on soybean deterioration. Following storage treatment, samples were held under aeration in a respirometer at 26°C and 21% moisture, and evolved Carbon Dioxide mass was measured until samples had lost 1.0% of original dry matter. At high harvest moistures, combine-harvested soybeans deteriorated faster, but at low harvest moistures, the deterioration rate of hand-harvested soybeans was greater. After 48 weeks of storage, the soybeans harvested at 22% moisture and preserved at -18°C deteriorated in a respirometer like freshly harvested soybeans, but soybeans harvested at 9% deteriorated in a respirometer significantly faster than those freshly harvested at 13% moisture.

  • Carbon Dioxide Evolution from High-Moisture Shelled Corn Treated with Iprodione †.
    Journal of food protection, 1995
    Co-Authors: Slaven Aljinovic, Carl J. Bern, N. Dugba, Manjit K. Misra
    Abstract:

    Carbon Dioxide Evolution was used to determine the storage life of 22.7% moisture shelled corn. Four iprodione fungicide treatments plus an untreated control were tested. The fungicide was tested on corn having three levels of mechanical kernel damage: 7% (hand shelled), 25% (combine harvested), and 16% (a blend of the other two damage levels). All iprodione treatments significantly increased storage life. Corn samples with higher levels of kernel damage took shorter times to reach the 0.5% dry-matter loss (DML) level. For combine-shelled corn, the fungicide increased storage life 17% at 15 mg/kg of corn and 46% at 20 mg/kg of corn.

  • Carbon Dioxide Evolution of Fungicide-treated High-moisture Corn
    Transactions of the ASAE, 1993
    Co-Authors: Sulaiman Alyahya, Carl J. Bern, Manjit K. Misra, Theodore B. Bailey
    Abstract:

    Two corn hybrids, one resistant (FR35 ¥ FR20) the other susceptible (DF20 ¥ DF12) to storage fungi, were harvested and hand-shelled at 22% moisture, wet basis, and stored at this moisture in aerated l-kg bin units. Four Rovral® fungicide treatments plus an untreated control were tested using Carbon Dioxide Evolution as the index of grain-deterioration rate. Equations of Carbon Dioxide weight versus time were fitted. The resistant corn hybrid manifested a lower deterioration rate than did the susceptible hybrid. Samples treated with fungicide showed a reduction in grain-deterioration rate compared with untreated samples.

Etienne Paul - One of the best experts on this subject based on the ideXlab platform.

  • Use of Carbon Dioxide Evolution rate for determining heterotrophic yield and characterising denitrifying biomass
    Water Science and Technology, 1999
    Co-Authors: Mathieu Spérandio, V. Urbain, J.m. Audic, Etienne Paul
    Abstract:

    The aim of this work was to show the potentiality of Carbon Dioxide Evolution rate measurement (CER) in characterisation of heterotrophic biomass, especially in anoxic conditions, in view of modelling and design denitrifying processes. The Carbon Dioxide Evolution rate (CER) was determined in a respirometer by infrared analysis associated to a modelling technique. During anoxic and aerobic batch experiments CER was qualitatively correlated with other respirometric methods (OUR and NUR) and with organic Carbon consumption. Yield coefficients were determined under aerobic (Y H ) and anoxic (Y HD ) conditions by means of Carbon balances using CER and organic Carbon measurements. Compared to the COD balances, accuracy of the yield estimation was improved and results obtained were not significantly different. Measured anoxic yields were systematically lower than aerobic ones, and the observed ratios between them were in the range from 0.66 to 0.85. By comparing aerobic and anoxic CER, two methods were proposed to determine the correction factor for anoxic growth η g . The first results obtained were consistent with those given by the classical method (NUR/OUR).

  • Determination of Carbon Dioxide Evolution rate using on-line gas analysis during dynamic biodegradation experiments.
    Biotechnology and bioengineering, 1997
    Co-Authors: Mathieu Spérandio, Etienne Paul
    Abstract:

    Respirometry is a precious tool for determining the activity of microbial populations. The measurement of oxygen uptake rate is commonly used but cannot be applied in anoxic or anaerobic conditions or for insoluble substrate. Carbon Dioxide production can be measured accurately by gas balance techniques, especially with an on-line infrared analyzer. Unfortunately, in dynamic systems, and hence in the case of short-term batch experiments, chemical and physical transfer limitations for Carbon Dioxide can be sufficient to make the observed Carbon Dioxide Evolution rate (OCER) deduced from direct gas analysis very different from the biological Carbon Dioxide Evolution rate (CER).To take these transfer phenomena into account and calculate the real CER, a mathematical model based on mass balance equations is proposed. In this work, the chemical equilibrium involving Carbon Dioxide and the measured pH Evolution of the liquid medium are considered. The mass transfer from the liquid to the gas phase is described, and the response time of the analysis system is evaluated.Global mass transfer coefficients (K(L)a) for Carbon Dioxide and oxygen are determined and compared to one another, improving the choice of hydrodynamic hypotheses. The equations presented are found to give good predictions of the disturbance of gaseous responses during pH changes.Finally, the mathematical model developed associated with a laboratory-scale reactor, is used successfully to determine the CER in nonstationary conditions, during batch experiments performed with microorganisms coming from an activated sludge system.

Cecilia Sundberg - One of the best experts on this subject based on the ideXlab platform.

  • Process inhibition due to organic acids in fed-batch composting of food waste – influence of starting culture
    Biodegradation, 2005
    Co-Authors: Cecilia Sundberg, Håkan Jönsson
    Abstract:

    Inhibition of the degradation during low pH conditions has been observed in fed-batch composting systems. To analyse this phenomenon, fed-batch composting of food waste with different amounts of starting culture was examined in laboratory reactor experiments. Changes in temperature, Carbon Dioxide Evolution, pH, solids, ash and short chain organic acids were measured. In reactors with a daily feed rate of 24% or less of the starting culture, thermophilic temperatures occurred and the pH and Carbon Dioxide Evolution were high and stable after a starting period of 4–5 days. In reactors with a daily feed rate of 48% or more of the starting culture the composting process failed, as the pH dropped below 6 and remained there and the temperature and Carbon Dioxide Evolution were low. It was concluded that the use of adequate amounts of starting culture consisting of active compost can efficiently prevent low pH conditions and process inhibition in fed-batch composting of food waste.

  • Process inhibition due to organic acids in fed-batch composting of food waste--influence of starting culture.
    Biodegradation, 2005
    Co-Authors: Cecilia Sundberg, Håkan Jönsson
    Abstract:

    Inhibition of the degradation during low pH conditions has been observed in fed-batch composting systems. To analyse this phenomenon, fed-batch composting of food waste with different amounts of starting culture was examined in laboratory reactor experiments. Changes in temperature, Carbon Dioxide Evolution, pH, solids, ash and short chain organic acids were measured. In reactors with a daily feed rate of 24% or less of the starting culture, thermophilic temperatures occurred and the pH and Carbon Dioxide Evolution were high and stable after a starting period of 4-5 days. In reactors with a daily feed rate of 48% or more of the starting culture the composting process failed, as the pH dropped below 6 and remained there and the temperature and Carbon Dioxide Evolution were low. It was concluded that the use of adequate amounts of starting culture consisting of active compost can efficiently prevent low pH conditions and process inhibition in fed-batch composting of food waste.