Determination of the effective diffusion coefficient of oxygen in gel materials in relation to gel concentration

Hulst, A.C.; Hens, H. J. H.; Buitelaar, R.M.; Tramper, J.

doi:10.1007/bf01875620

Cited by 57 publications

(32 citation statements)

References 5 publications

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“…The details of microelectrode measurements are described elsewhere (26,27). Based on the O 2 and NH 4 ϩ concentration profiles measured, the total O 2 and NH 4 ϩ consumption rates were calculated using Fick's first law of diffusion (26,27 for O 2 in 3% agar plate at 20°C (16). Differences between the rates were statistically analyzed by t test.…”

Section: Methodsmentioning

confidence: 99%

Influences of Infaunal Burrows on the Community Structure and Activity of Ammonia-Oxidizing Bacteria in Intertidal Sediments

Satoh

Nakamura

Okabe

2007

Appl Environ Microbiol

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Influences of infaunal burrows constructed by the polychaete (Tylorrhynchus heterochaetus) on O 2 concentrations and community structures and abundances of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in intertidal sediments were analyzed by the combined use of a 16S rRNA gene-based molecular approach and microelectrodes. The microelectrode measurements performed in an experimental system developed in an aquarium showed direct evidence of O 2 transport down to a depth of 350 mm of the sediment through a burrow. The 16S rRNA gene-cloning analysis revealed that the betaproteobacterial AOB communities in the sediment surface and the burrow walls were dominated by Nitrosomonas sp. strain Nm143-like sequences, and most of the clones in Nitrospira-like NOB clone libraries of the sediment surface and the burrow walls were related to the Nitrospira marina lineage. Furthermore, we investigated vertical distributions of AOB and NOB in the infaunal burrow walls and the bulk sediments by real-time quantitative PCR (Q-PCR) assay. The AOB and Nitrospira-like NOB-specific 16S rRNA gene copy numbers in the burrow walls were comparable with those in the sediment surfaces. These numbers in the burrow wall at a depth of 50 to 55 mm from the surface were, however, higher than those in the bulk sediment at the same depth. The microelectrode measurements showed higher NH 4 ؉ consumption activity at the burrow wall than those at the surrounding sediment. This result was consistent with the results of microcosm experiments showing that the consumption rates of NH 4 ؉ and total inorganic nitrogen increased with increasing infaunal density in the sediment. These results clearly demonstrated that the infaunal burrows stimulated O 2 transport into the sediment in which otherwise reducing conditions prevailed, resulting in development of high NH 4 ؉ consumption capacity. Consequently, the infaunal burrow became an important site for NH 4 ؉ consumption in the intertidal sediment.Benthic infaunal activities, such as burrow formation, burrow irrigation, defecation, and excretion of soluble and insoluble metabolites, increase the surface area across which solutes can diffuse into or out of the sediments and the substrate availability for inhabiting microorganisms (5,13,17,24,25,32,34). These burrows also provide a more stable physical environment compared to bulk sediment. Therefore, the sediment surrounding the infaunal burrows (i.e., burrow walls) could have markedly higher levels of microbial biomass, diversity, and activity compared with the bulk sediment. Previous studies have revealed that benthic infaunal activities resulted in changes in biogeochemical characteristics and microbial community structures in sediments (20,22,31). Although many studies demonstrated that the presence of benthic infauna strongly affects the microbial ecology of estuarine sediments, surprisingly little attention has been paid to bioturbation effects on nitrification. In estuarine systems with high inputs of nitrogenous compounds, sedim...

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Section: Methodsmentioning

confidence: 99%

Influences of Infaunal Burrows on the Community Structure and Activity of Ammonia-Oxidizing Bacteria in Intertidal Sediments

Satoh

Nakamura

Okabe

2007

Appl Environ Microbiol

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“…In a review of seven studies in which the diffusivity of oxygen was measured in various types of hydrogels (mostly alginate and agarose), values of the diffusivity in the hydrogel (D) ranged from 25% to 99% of D aq , with a mean of 78% (Beuling et al, 2000;Hiemstra et al, 1983;Hulst et al, 1989;Kurosawa et al, 1989;Li et al, 1996;Sato and Toda, 1983;Sun and Furusaki, 1989). Regrettably, none of these studies investigated collagen gels such as those used in EHTs, but the similarities in transport measurements between different hydrogels implies that there is minimal reaction of oxygen with the gel fibers, and that the pertinent characteristics for diffusion relate to the path length in the hydrogel rather than the chemistry of the polymer constituent.…”

Section: Anisotropic Diffusivitymentioning

confidence: 99%

Analysis of oxygen transport in a diffusion‐limited model of engineered heart tissue

Brown

MacLellan

Laks

et al. 2007

Biotech & Bioengineering

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Cardiac tissue engineering has made notable progress in recent years with the advent of an experimental model based on neonatal cardiomyocytes entrapped in collage gels and purified basement membrane extract, known as "engineered heart tissues" (EHTs). EHTs are a formidable display of tissue-level contractile function and cellular-level differentiation, although they suffer greatly from mass transport limitations due to the high density of metabolically active cells and the diffusion-limited nature of the hydrogel. In this report, a mathematical model was developed to predict oxygen levels inside a one-dimensional, diffusion-limited model of EHT. These predictions were then compared to values measured in corresponding experiments with a hypoxia-sensitive stain (pimonidazole). EHTs were cast between two plastic discs, which allowed for mass transfer with the culture medium to occur in only the radial direction. EHTs were cultured for up to 36 h in the presence of pimonidazole, after which time they were snap-frozen, histologically sectioned, and stained for bound pimonidazole. Quantitative image analysis was performed to measure the distance from the culture medium at which hypoxia first occurs under various conditions. As tested by variation of simple design parameters, the trends in oxygen profiles predicted by the model are in reasonable agreement with those obtained experimentally, although a number of ambiguities related to the specific model parameters led to a general overprediction of oxygen concentrations. Based on the sensitivity analysis in the present study, it is concluded that diffusion-reaction models may offer relatively precise predictions of oxygen concentrations in diffusion-limited tissue constructs.

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“…The effective diffusion coefficient for oxygen in tc-carrageenan beads was determined by Hulst et al 24 Up to a polymer concentration of 3% a constant effective diffusivity of 1.58 x m2 . s-' was found.…”

Section: Effective Diffusion Coefficient (Djmentioning

confidence: 99%

Growth and substrate consumption of Nitrobacter agilis cells immobilized in carrageenan: Part 2. Model evaluation

Wijffels¹,

Gooijer²,

Kortekaas³

et al. 1991

Biotech & Bioengineering

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114

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A dynamic model that predicts substrate and biomass concentration profiles across gel beads and from that the overall substrate consumption rate by the gel beads containing growing cells was evaluated with immobilized Nitrobacter agilis cells in an airlift loop reactor with oxygen as the limiting substrate. The model predictions agreed well with the observed oxygen consumption rates at three different liquid phase oxygen concentrations. Image analysis showed that 90% of the immobilized cells after 42 days of cultivation was situated in the outer shells in a film of 140 mum, while the bead radius was about 1 mm. The maximum biomass concentration in the outmost film of 56 mum was 11 kg . m(-3) gel.

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Determination of the effective diffusion coefficient of oxygen in gel materials in relation to gel concentration

Cited by 57 publications

References 5 publications

Influences of Infaunal Burrows on the Community Structure and Activity of Ammonia-Oxidizing Bacteria in Intertidal Sediments

Influences of Infaunal Burrows on the Community Structure and Activity of Ammonia-Oxidizing Bacteria in Intertidal Sediments

Analysis of oxygen transport in a diffusion‐limited model of engineered heart tissue

Growth and substrate consumption of Nitrobacter agilis cells immobilized in carrageenan: Part 2. Model evaluation

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