Calcium-alginate immobilized cell systems were developed for the detoxification and biodegradation of coumaphos, an organophosphate insecticide, and its hydrolysis products, chlorferon and ...diethlythiophosphate (DETP). Optimum bead loadings for bioreactor operation were found to be 200
g-beads/L for chlorferon degradation and 300
g-beads/L for DETP degradation. Using waste cattle dip (UCD) solution as substrate, the degradation rate for an immobilized consortium of chlorferon-degrading bacteria was five times greater than that for freely suspended cells, and hydrolysis of coumaphos by immobilized OPH
+
Escherichia coli was 2.5 times greater. The enhanced degradation of immobilized cells was due primarily to protection of the cells from inhibitory substances present in the UCD solution. In addition, physiological changes of the cells caused by Ca-alginate immobilization may have contributed to increased reaction rates. Degradation rates for repeated operations increased for successive batches indicating that cells became better adapted to the reaction conditions over time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Diffusion characteristics of chlorferon and diethylthiophosphate (DETP) in Ca-alginate gel beads were studied to assist in designing and operating bioreactor systems. Diffusion coefficients for ...chlorferon and DETP in Ca-alginate gel beads determined at conditions suitable for biodegradation studies were 2.70 x 10⁻¹¹ m²/s and 4.28 x 10⁻¹¹ m²/s, respectively. Diffusivities of chlorferon and DETP were influenced by several factors, including viscosity of the bulk solution, agitation speed, and the concentrations of diffusing substrate and immobilized cells. Diffusion coefficients increased with increasing agitation speed, probably due to poor mixing at low speed and some attrition of beads at high speeds. Diffusion coefficients also increased with decreasing substrate concentration. Increased cell concentration in the gel beads caused lower diffusivity. Theoretical models to predict diffusivities as a function of cell weight fraction overestimated the effective diffusivities for both chlorferon and DETP, but linear relations between effective diffusivity and cell weight fraction were derived from experimental data. Calcium-alginate gel beads with radii of 1.65-1.70 mm used in this study were not subject to diffusional limitations: external mass transfer resistances were negligible based on Biot number calculations and effectiveness factors indicated that internal mass transfer resistance was negligible. Therefore, the degradation rates of chlorferon and DETP inside Ca-alginate gel beads were reaction-limited. Biotechnol. Bioeng. 2008;100: 698-706.
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Chlorferon and diethylthiophosphate (DETP) are the hydrolysis products of coumaphos, an organophosphate pesticide. In this research, two consortia of bacterial cultures, one responsible for degrading ...chlorferon and the other for degrading DETP, were selectively enriched from waste cattle dip solution. The enriched cultures were used as inocula to grow biomass for biodegradation studies. For chlorferon degradation, the optimum biomass concentration was found to be 80
g/L, and pH 7.5 was selected as the optimal operating pH. Chlorferon degradation was characterized by substrate inhibition kinetics with parameter values estimated to be
V
m
=
0.062
±
0.011
mg/(g-biomass)
h,
K
m
=
21
±
7
mg/L, and
K
Si
=
118
±
45
mg/L. For DETP degradation, the optimum biomass concentration was found to be 60
g/L, and the optimum pH was in the range of 7.5–8. DETP degradation was characterized by Michaelis–Menten kinetics with parameter values estimated to be
V
m
=
1.52
±
0.10
mg/(g-biomass)
h and
K
m
=
610
±
106
mg/L.
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4.
Kinetic Models for Growth and Product Formation on Multiple Substrates Kwon, Y.J. (Kyonggi University, Suwon, Republic of Korea), E-mail: yjkwon@kyonggi.ac.kr; Engler, Cady R. (Texas AnM University, TX, USA)
Biotechnology and bioprocess engineering,
12/2005, Volume:
10, Issue:
6
Journal Article
Peer reviewed
Hydrolyzates from lignocellulosic biomass contain a mixture of simple sugars; the predominant ones being glucose, cellobiose and xylose. The fermentation of such mixtures to ethanol or other ...chemicals requires an understanding of how each of these substrates is utilized. Candida Iusitaniae can efficiently produce ethanol from both glucose and cellobiose and is an attractive organism for ethanol production. Experiments were performed to obtain kinetic data for ethanol production from glucose, cellobiose and xylose.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A batch anaerobic composting process was investigated to evaluate the potential for biogas recovery from animal manure under the worst scenario of high initial solids and non-well adapted ...microorganisms. The effects of composting time and initial total solids content on biogas recovery and reduction of solids during anaerobic digestion of swine, poultry and beef manure were studied. Volatile solids reductions averaged 10% or less over a 30-day period for all initial solids contents, which was considerably lower than expected. Reductions in VS increased slightly as initial solids content in the reactor decreased. Reductions in COD were somewhat higher than for VS. The pH values were fairly stable during the composting experiments and within the range suitable for anaerobic digestion. Decreases in TKN and ammonia nitrogen during the process were insignificant, and greater decreases were observed for lower initial solids content in the reactors. Cumulative biogas production increased with decreasing solids content in the reactor for all types of manure. For the lowest initial solids contents (12-14%), swine manure produced more biogas, but at the higher initial solids contents there was little difference among the manure types. Biogas yields were about 0.5 m /kg VS consumed for the lowest solids contents; however, yields were only about 0.2 m /kg VS consumed for the higher initial solids. Methane content of the biogas samples averaged 49%. Based on these results, it appears that adapting microbial populations in the high solids feedstock may obtain reasonable biogas production rates and VS reduction during anaerobic digestion. Although some differences in results among the three types of manure were noted, they were not large and likely would not be significant with adapted microbial populations.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Pesticide wastes generated from livestock dipping operations containing the organophosphate (OP) insecticide coumaphos (CP) are well suited for disposal by biodegradation since they are highly ...concentrated (∼1 g/L), generally contained, and lack additional toxic components. In this study, a significantly enhanced efficiency of degrading CP in cattle dip waste (CDW) is reported using a dense, nongrowing cell population that functions without the addition of nutrients required for growing cell cultures. A recombinant strain of Escherichia coli containing the opd gene for organophosphate hydrolase (OPH), which is capable of active hydrolysis of OP neurotoxins including CP, was cultivated in a rich medium containing all essential nutrients. Cells were harvested and utilized in lab scale experiments in the form of either freely suspended cells or cells immobilized within a macroporous gel matrix, poly(vinyl alcohol) (PVA) cryogel. Significantly higher degradation rates were achieved with either suspended or immobilized OPH+ cells compared to rates with the microbial consortium naturally present in CDW. Of the two nongrowing cell systems, the detoxification rate with immobilized cells was approximately twice that of freely suspended cells, and kinetic studies demonstrated that a higher maximum reaction rate was achieved with the immobilized cell system. A comparative study using both the CDW and pure CP substrates with free cells indicated that the CDW contained one or more factors that reduced the bioavailability of CP. The immobilized cells retained their activity over a 4‐month period of use and storage, demonstrating both sustained catalytic activity and long‐term mechanical stability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Hydrolyzates from lignocellulosic biomass contain a mixture of simple sugars; the predominant ones being glucose, cellobiose and xylose. The fermentation of such mixtures to ethanol or other ...chemicals requires an understanding of how each of these substrates is utilized. Candida lusitaniae can efficiently produce ethanol from both glucose and cellobiose and is an attractive organism for ethanol production. Experiments were performed to obtain kinetic data for ethanol production from glucose, cellobiose and xylose. Various combinations were tested in order to determine kinetic behavior with multiple carbon sources. Glucose was shown to repress the utilization of cellobiose and xylose. However, cellobiose and xylose were simultaneously utilized after glucose depletion. Maximum volumetric ethanol production rates were 0.56, 0.33, and 0.003 g/L h from glucose, cellobiose and xylose, respectively. A kinetic model based on cAMP mediated catabolite repression was developed. This model adequately described the growth and ethanol production from a mixture of sugars in a batch culture.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Diffusion characteristics of chiorferon and diethyithiophosphate (DETP) in Ca-alginate gel beads were studied to assist in designing and operating bioreactor systems. Diffusion coefficients for ...chlorferon and DETP in Ca-alginate gel beads determined at conditions suitable for biodegradation studies were 2.70 x 10... m.../s and 4.28 x 10... m.../s, respectively. Diffusivities of chlorferon and DETP were influenced by several factors, including viscosity of the bulk solution, agitation speed, and the concentrations of diffusing substrate and immobilized cells. Diffusion coefficients increased with increasing agitation speed, probably due to poor mixing at low speed and some attrition of beads at high speeds. Diffusion coefficients also increased with decreasing substrate concentration. Increased cell concentration in the gel beads caused lower diffusivity. Theoretical models to predict diffusivities as a function of cell weight fraction overestimated the effective diffusivities for both chlorferon and DETP, but linear relations between effective diffusivity and cell weight fraction were derived from experimental data. Calcium-alginate gel beads with radii of 1.65-1.70 mm used in this study were not subject to diffusional limitations: external mass transfer resistances were negligible based on Biot number calculations and effectiveness factors indicated that internal mass transfer resistance was negligible. Therefore, the degradation rates of chlorferon and DETP inside Ca-alginate gel beads were reaction-limited. (ProQuest: ... denotes formulae/symbols omitted.)
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The goal of this research was to determine the potential of the fungal sterol ergosterol as an indicator of fungal biomass and to determine the growth response of the transformed strain of T. virens ...(GvT6) to added substrate and changes in temperature. Experiments in liquid culture and agar plates containing a rich medium of glucose, yeast extract, and casein (GYEC), or a soil extract medium supplemented with maltose (SE) showed that the ergosterol content of GvT6 was greatest when grown on GYEC agar plates (14.02 mg/g dry biomass). For both media, plate cultures produced higher specific ergosterol values than liquid cultures. Changes in specific ergosterol values over time were generally not significant. A value of 5.41 mg ergosterol / g dry biomass, determined for SE plate cultures, was used to convert ergosterol values to biomass values in growth experiments in soil bioreactors.
Data from experiments in soil bioreactors treated with different levels of substrate (0.5-8 mg maltose / g dry soil) at three different temperatures (22, 27, 32°C) showed subsurface growth of GvT6 can be described by the logistic equation. Culture conditions of 32°C and 8 mg/g substrate produced the highest levels of biomass, but growth at 32°C and 4 mg/g substrate was somewhat faster than at the higher substrate level.
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Modeling methods used to optimize the biocatalytic efficiency of freely suspended cells have been applied to non‐growing microbial cells entrapped within a macro‐porous carrier. The catalytic rate, ...which is dependent on cell concentration inside the biocatalyst beads, coincided with catalytic parameters for freely suspended cells. Immobilized non‐growing cell systems could be optimized utilizing the characteristics of freely suspended cells without requiring extensive experimentation to define catalytic behaviour inside the biocatalyst. A dynamic diffusion–reaction model was developed and validated using experimental data for thiodiglycol degradation by Alcaligenes xylosoxidans subsp. xylosoxidans immobilized within macro‐porous poly(vinyl alcohol) cryogel in a completely mixed batch bioreactor.
Des mèthodes de modèlisation visant à optimiser l'efficacitè biocatalytique de cellules en suspension libre ont ètè appliquèes à des cellules microbiennes qui ne sont pas en croissance piègèes dans un support macro‐poreux. La vitesse catalytique, qui est dèpendante de la concentration de cellules dans les billes de biocatalyseur, coincide avec les parameátres catalytiques pour les cellules en suspension libre. Des systeámes de cellules immobilisèes qui ne sont pas en croissance pourraient ětre immobilisès à l'aide des caractèristiques des cellules en suspension libre sans nècessiter une expèrimentation poussèe pour dèfinir le comportement catalytique dans le biocatalyseur. Un modeále de diffusion‐rèaction dynamique a ètè mis au point et validè à l'aide de donnèes expèrimentales pour la dègradation du thiodiglycol par les xylosoxidans de la sous‐espeáce Alcaligenes xylosoxidans immobilisès dans un cryogel de poly(alcool de vinyle) dans un rèacteur discontinu compleátement mèlangè.
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