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Yield Coefficients (yield + coefficient)

Distribution by Scientific Domains

Life Sciences	73%
Chemistry	26%

Selected Abstracts

The fermentation stoichiometry of Thermotoga neapolitana and influence of temperature, oxygen, and pH on hydrogen production

BIOTECHNOLOGY PROGRESS, Issue 4 2009
Sarah A. Munro
Abstract The hyperthermophilic bacterium, Thermotoga neapolitana, has potential for use in biological hydrogen (H2) production. The objectives of this study were to (1) determine the fermentation stoichiometry of Thermotoga neapolitana and examine H2 production at various growth temperatures, (2) investigate the effect of oxygen (O2) on H2 production, and (3) determine the cause of glucose consumption inhibition. Batch fermentation experiments were conducted at temperatures of 60, 65, 70, 77, and 85°C to determine product yield coefficients and volumetric productivity rates. Yield coefficients did not show significant changes with respect to growth temperature and the rate of H2 production reached maximum levels in both the 77°C and 85°C experiments. The fermentation stoichiometry for T. neapolitana at 85°C was 3.8 mol H2, 2 mol CO2, 1.8 mol acetate, and 0.1 mol lactate produced per mol of glucose consumed. Under microaerobic conditions H2 production did not increase when compared to anaerobic conditions, which supports other evidence in the literature that T. neapolitana does not produce H2 through microaerobic metabolism. Glucose consumption was inhibited by a decrease in pH. When pH was adjusted with buffer addition cultures completely consumed available glucose. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

The Auxiliary Substrate Concept: From simple considerations to heuristically valuable knowledge

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2009
Wolfgang Babel
Abstract Microorganisms are used in biotechnology. They are either (i) aim and purpose of a process, e.g. with the production of single cell proteins, or (ii) mean to an end insofar as they serve as a catalyst or "factory" for syntheses (e.g. of products of primary and secondary metabolism, of enzymes and antibiotics) or for the degradation and detoxification of harmful organics and inorganics. In all cases, the efficiency and velocity, finally the productivity, are parameters which essentially determine the economy of the processes. Therefore, search for approaches to optimize these processes is a permanent task and challenge for scientists and engineers. It is shown that the auxiliary substrate concept is suitable to increase the yield coefficients. It is based on the energetic evaluation of organics, on the knowledge that organics as sources of carbon and energy for growth are deficient in ATP and/or reducing equivalents, and says that it is possible to improve the carbon conversion efficiency up to the carbon metabolism determined upper limit. The latter is determined by inevitable losses of carbon along the way of assimilation and anabolism and amounts to about 85% for so-called glycolytic substrates, e.g. glucose, methanol, and to about 75% for gluconeogenetic substrates, e.g. C2 -substrates (acetic acid, hexadecane). The approach is explained and some experimental examples are presented. By simultaneous utilization of an extra energy source (auxiliary substrate) the yield coefficient can be increased (i) in glucose from about 0.5 to 0.7,g/g (by means of formate), (ii) in acetate from 0.34,0.4 to 0.5,0.65,g/g (by means of formate and thiosulfate, respectively), and (iii) in hexadecane from about 0.94 to 1.26,g/g (by means of formate). The precalculated yield coefficients and mixing ratios agree well with the experimentally attained ones. The approach is easily feasible and economically valuable. [source]

Production of PHB from Crude Glycerol

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2007
G. Mothes
Abstract Crude glycerol , a by-product of the large scale production of diesel oil from rape , is examined for its possible use as a cheap feedstock for the biotechnological synthesis of poly(3-hydroxybutyrate) (PHB). The glycerol samples of various manufacturers differ in their contamination with salts (NaCl or K2SO4), methanol or fatty acids. At high cell density fermentation these pollutants could possibly accumulate to inhibiting concentrations. The bacteria used were Paracoccus denitrificans and Cupriavidus necator JMP 134, which accumulate PHB from pure glycerol to a content of 70 % of cell dry mass. When using crude glycerol containing 5.5 % NaCl, a reduced PHB content of 48 % was observed at a bacterial dry mass of 50 g/L. Furthermore the PHB yield coefficient was reduced, obviously due to osmoregulation. The effect of glycerol contaminated with K2SO4 was less pronounced. The molecular weight of PHB produced with P. denitrificans or C. necator from crude glycerol varies between 620000 and 750000 g/mol which allows the processing by common techniques of the polymer industry. [source]

Influence of heavy metals on microbial growth kinetics including lag time: Mathematical modeling and experimental verification,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2009
S. Sevinç, engör
Abstract Heavy metals can significantly affect the kinetics of substrate biodegradation and microbial growth, including lag times and specific growth rates. A model to describe microbial metabolic lag as a function of the history of substrate concentration has been previously described by Wood et al. (Water Resour Res 31:553,563) and Ginn (Water Resour Res 35:1395,1408). In the present study, this model is extended by including the effect of heavy metals on metabolic lag by developing an inhibitor-dependent functional to account for the metabolic state of the microorganisms. The concentration of the inhibiting metal is explicitly incorporated into the functional. The validity of the model is tested against experimental data on the effects of zinc on Pseudomonas species isolated from Lake Coeur d'Alene sediments, Idaho, USA, as well as the effects of nickel or cobalt on a mixed microbial culture collected from the aeration tank of a wastewater treatment plant in Athens, Greece. The simulations demonstrate the ability to incorporate the effect of metals on metabolism through lag, yield coefficient, and specific growth rates. The model includes growth limitation due to insufficient transfer of oxygen into the growth medium. [source]

Influence of nutritional conditions on the mycelial growth and exopolysaccharide production in Paecilomyces sinclairii

LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2002
S.W. Kim
Aims:,The objective of the study was to optimize the submerged culture conditions for the production of exopolysaccharide from Paecilomyces sinclairii. Methods and Results:,The optimal temperature and initial pH for exopolysaccharide production by Paecilomyces sinclairii in shake flask culture were found to be 30°C and 6·0, respectively. Sucrose (60 g l,1) and corn steep powder (10 g l,1) were the most suitable carbon and nitrogen source for exopolysaccharide production. Conclusions:,Under optimal culture medium, the maximum exopolysaccharide concentration in a 5-l stirred-tank fermenter indicated 7·4 g l,1, which was approximately three times higher than that in basal medium. The maximum specific growth rates (,max) and yield coefficient (YP/S) in the optimal culture medium was 0·16 h,1 and 0·19, respectively. Significance and Impact of the Study:,The optimal culture conditions reported in this article can be widely applied to the processes for submerged cultures of other mushrooms. [source]

Kinetic Study of the Conversion of Different Substrates to Lactic Acid Using Lactobacillus bulgaricus

BIOTECHNOLOGY PROGRESS, Issue 3 2000
Concepción N. Burgos-Rubio
Lactic acid fermentation includes several reactions in association with the microorganism growth. A kinetic study was performed of the conversion of multiple substrates to lactic acid using Lactobacillusbulgaricus. Batch experiments were performed to study the effect of different substrates (lactose, glucose, and galactose) on the overall bioreaction rate. During the first hours of fermentation, glucose and galactose accumulated in the medium and the rate of hydrolysis of lactose to glucose and galactose was faster than the convesion of these substrates. Once the microorganism built the necessary enzymes for the substrate conversion to lactic acid, the conversion rate was higher for glucose than for galactose. The inoculum preparation was performed in such a way that healthy young cells were obtained. By using this inoculum, shorter fermentation times with very little lag phase were observed. The consumption patterns of the different substrates converted to lactic acid were studied to determine which substrate controls the overall reaction for lactic acid production. A mathematical model (unstructured Monod type) was developed to describe microorganism growth and lactic acid production. A good fit with a simple equation was obtained. It was found experimentally that the approximate ratio of cell to substrate was 1 to 10, the growth yield coefficient (YXS) was 0.10 g cell/g substrate, the product yield (YPS) was 0.90 g lactic acid/g substrate, and the , parameter in the Luedeking-Piret equation was 9. The Monod kinetic parameters were obtained. The saturation constant (KS) was 3.36 g/L, and the specific growth rate (,m ) was 1.14 l/h. [source]

The Auxiliary Substrate Concept: From simple considerations to heuristically valuable knowledge

Anaerobic biodegradation of two-phase olive mill solid wastes and liquid effluents: kinetic studies and process performance

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2006
Rafael Borja
Abstract The new two-phase olive oil mills produce three identifiable and separate waste streams, namely (1) the wash waters from the initial cleansing of the fruit, (2) the aqueous solid residues from the primary centrifugation and (3) the wash waters from the secondary centrifugation. As well as offering process advantages, they also consume less water. Therefore the solid residue, two-phase olive mill solid waste (OMSW), has a high organic matter concentration, giving it an elevated polluting load, and cannot be easily handled by traditional technology which deals with the conventional three-phase olive cake. In addition, the new two-phase olive mill effluents (TPOME) are made up of a mixture of effluents (1) and (3), the total volume of TPOME generated being ,0.25 dm3 kg,1 olives processed. This review aims to report the main features and characteristics of two-phase OMSW and TPOME as compared with the classical olive cake and olive mill wastewater (OMW) derived from the three-phase manufacturing process. The advantages and disadvantages of the two-phase decanting process are summarised. The anaerobic digestibility of two-phase OMSW using different influent substrate concentrations is reported. Kinetic studies of anaerobic digestion of two-phase OMSW are also reviewed and summarised, as well as mass balances to predict the behaviour of the reactor and simplified kinetic models for studying the hydrolysis, acidogenic and methanogenic steps of one- and two-stage anaerobic digestion of OMSW. The review also includes the following: assays of anaerobic digestion of wastewaters from the washing of olives, of olive oil and the two together using fluidised beds and hybrid reactors; the kinetics, performance, stability, purification efficiencies and methane yield coefficients. Copyright © 2006 Society of Chemical Industry [source]

Oxygen transfer effects in ,-lactamase fermentation by Bacillus licheniformis in a glucose-based defined medium

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005
nar Çal
Abstract The effects of oxygen transfer on the ,-lactamase production by Bacillus licheniformis were investigated in a glucose-based defined medium. The experiments were conducted in 3.0 dm3 batch bioreactor systems at three different air inlet (QO/VR = 0.2, 0.5 and 1.0 vvm) and agitation rates (N = 250, 500 and 750 min,1). During the fermentation, the concentrations of the cell, glucose, by-products, ie organic and amino acids, oxygen transfer coefficients (KLa), yield coefficients, specific rates and oxygen uptake rates (OUR) were determined, in addition to ,-lactamase activities. The highest ,-lactamase activity was obtained at QO/VR = 0.5 vvm and N = 500 min,1 and at QO/VR = 0.2 vvm and N = 500 min,1 conditions, as caA = 90 U cm,3. The highest cell concentration was obtained as CX = 0.67 kg m,3 at QO/VR = 0.5 vvm and N = 750 min,1 and at QO/VR = 0.2 vvm and N = 750 min,1 conditions. The values of KLa increased with increasing agitation and aeration rates and varied between 0.007 and 0.044 s,1, and the OUR varied between 0.4 and 1.6 mol m,3 s,1. With increasing QO/VR and/or N, the Damköhler number (ie the oxygen transfer limitation) decreased owing to the increase in mass transfer coefficients (KLa). The highest instantaneous yield of cell on substrate (YX/S) and yield of cell on oxygen (YX/O) values were respectively obtained at 0.5 vvm and 500 min,1 conditions at t = 2 h as YX/S = 0.72 kg kg,1 and YX/O = 1.49 kg kg,1. The highest instantaneous yield of substrate on oxygen (YS/O) was obtained at 0.5 vvm and 750 min,1 conditions at t = 20 h as YS/O = 8.07 kg kg,1. Copyright © 2005 Society of Chemical Industry [source]

Efficiency of naphthalene biodegradation by Pseudomonas putida G7 in soil

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2004
Andrei E Filonov
Abstract The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene-degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean-up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry [source]

Municipal sludge degradation kinetic in thermophilic CSTR

AICHE JOURNAL, Issue 12 2006
Ángeles de la Rubia
Abstract The performance of a pilot-scale continuous-flow stirred-tank reactor (CSTR) treating municipal sludge under thermophilic conditions has been studied. Two pilot-scale reactors (CSTR1 (175 L) and CSTR2 (850 L)) were operated at different hydraulic residence times (,: 40 to 15 days). The anaerobic sludge processes are generally affected by variations in the concentration of substrate (determined as influent volatile solids, VS) and volumetric flow, both of which lead to a modification in biomass concentration and VS removal efficiency. This unsteady-state situation is mathematically explained in terms of an autocatalytic kinetic model. The general kinetic equation in this model has been applied to experimental data obtained in CSTR1. The fit of the experimental data to the model was used to estimate kinetic parameters and the yield coefficients (,max, ,, YP/S). The estimated parameters were ,max: 0.175d,1, ,: 0.358, YP/S: 0.309 m3CH4/kgVS). These parameters were subsequently used to model the substrate utilization rate and the methane generation rate in CSTR2. The model with the estimated parameters was found to provide excellent results, and is satisfactory in describing the concentration of VS and the methane generation rate in an actual digestion plant. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

Prediction of metabolic function from limited data: Lumped hybrid cybernetic modeling (L-HCM)

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010
Hyun-Seob Song
Abstract Motivated by the need for a quick quantitative assessment of metabolic function without extensive data, we present an adaptation of the cybernetic framework, denoted as the lumped hybrid cybernetic model (L-HCM), which combines the attributes of the classical lumped cybernetic model (LCM) and the recently developed HCM. The basic tenet of L-HCM and HCM is the same, that is, they both view the uptake flux as being split among diverse pathways in an optimal way as a result of cellular regulation such that some chosen metabolic objective is realized. The L-HCM, however, portrays this flux distribution to occur in a hierarchical way, that is, first among lumped pathways, and next among individual elementary modes (EM) in each lumped pathway. Both splits are described by the cybernetic control laws using operational and structural return-on-investments, respectively. That is, the distribution of uptake flux at the first split is dynamically regulated according to environmental conditions, while the subsequent split is based purely on the stoichiometry of EMs. The resulting model is conveniently represented in terms of lumped pathways which are fully identified with respect to yield coefficients of all products unlike classical LCMs based on instinctive lumping. These characteristics enable the model to account for the complete set of EMs for arbitrarily large metabolic networks despite containing only a small number of parameters which can be identified using minimal data. However, the inherent conflict of questing for quantification of larger networks with smaller number of parameters cannot be resolved without a mechanism for parameter tuning of an empirical nature. In this work, this is accomplished by manipulating the relative importance of EMs by tuning the cybernetic control of mode-averaged enzyme activity with an empirical parameter. In a case study involving aerobic batch growth of Saccharomyces cerevisiae, L-HCM is compared with LCM. The former provides a much more satisfactory prediction than the latter when parameters are identified from a few primary metabolites. On the other hand, the classical model is more accurate than L-HCM when sufficient datasets are involved in parameter identification. In applying the two models to a chemostat scenario, L-HCM shows a reasonable prediction on metabolic shift from respiration to fermentation due to the Crabtree effect, which LCM predicts unsatisfactorily. While L-HCM appears amenable to expeditious estimates of metabolic function with minimal data, the more detailed dynamic models [such as HCM or those of Young et al. (Young et al., Biotechnol Bioeng, 2008; 100: 542,559)] are best suited for accurate treatment of metabolism when the potential of modern omic technology is fully realized. However, in view of the monumental effort surrounding the development of detailed models from extensive omic measurements, the preliminary insight into the behavior of a genotype and metabolic engineering directives that can come from L-HCM is indeed valuable. Biotechnol. Bioeng. 2010;106: 271,284. © 2010 Wiley Periodicals, Inc. [source]

The fermentation stoichiometry of Thermotoga neapolitana and influence of temperature, oxygen, and pH on hydrogen production

A robust method for the joint estimation of yield coefficients and kinetic parameters in bioprocess models

BIOTECHNOLOGY PROGRESS, Issue 3 2009
V. Vastemans
Abstract Bioprocess model structures that require nonlinear parameter estimation, thus initialization values, are often subject to poor identification performances because of the uncertainty on those initialization values. Under some conditions on the model structure, it is possible to partially circumvent this problem by an appropriate decoupling of the linear part of the model from the nonlinear part of it. This article provides a procedure to be followed when these structural conditions are not satisfied. An original method for decoupling two sets of parameters, namely, kinetic parameters from maximum growth, production, decay rates, and yield coefficients, is presented. It exhibits the advantage of requiring only initialization of the first subset of parameters. In comparison with a classical nonlinear estimation procedure, in which all the parameters are freed, results show enhanced robustness of model identification with regard to parameter initialization errors. This is illustrated by means of three simulation case studies: a fed-batch Human Embryo Kidney cell cultivation process using a macroscopic reaction scheme description, a process of cyclodextrin-glucanotransferase production by Bacillus circulans, and a process of simultaneous starch saccharification and glucose fermentation to lactic acid by Lactobacillus delbrückii, both based on a Luedeking-Piret model structure. Additionally, perspectives of the presented procedure in the context of systematic bioprocess modeling are promising. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]