The determination of effective diffusion coefficients in a polysaccharide matrix used for the immobilization of biocatalysts

Grünwald, Peter; Hansen, K.; Gunßer, W.

doi:10.1016/s0167-2738(97)00373-1

Cited by 24 publications

(9 citation statements)

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“…Unfortunately Table 1 Siderophore activity ((a) and (b)) and specific siderophore activity ((c) and (d)) of free Pseudomonas aeruginosa and P. fluorescens cells cultivated in the presence of Fe and/or TM and supplied with either fructose, glycerol, mannitol or skim milk (concentration C2) all the substrates, except skim milk, released from beads until their concentrations equilibrated with the bulk liquid medium (data not shown). Indeed diffusion coefficients of glucose, fructose, sucrose and lactose in Ca-alginate membrane liquid-core capsules and in Ca-alginate beads immobilizing microorganisms were shown to be only 5-20% lower than the corresponding diffusivity in water [52,53] which explained why the concentration of solute in the bulk liquid medium reached equilibrium after a few minutes. The same conclusion was drawn by Duquenne et al [29] who suggested that diffusion of glycerol from microgranules to the soil limited the competitive advantage of such location effect.…”

Section: Co-location Of Carbon Substrates and Bacteria In Alginate Beadsmentioning

confidence: 94%

Impact of substrates and cell immobilization on siderophore activity by Pseudomonads in a Fe and/or Cr, Hg, Pb containing-medium

Braud¹,

Jézéquel²,

Lebeau³

2007

Journal of Hazardous Materials

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Section: Co-location Of Carbon Substrates and Bacteria In Alginate Beadsmentioning

confidence: 94%

Impact of substrates and cell immobilization on siderophore activity by Pseudomonads in a Fe and/or Cr, Hg, Pb containing-medium

Braud¹,

Jézéquel²,

Lebeau³

2007

Journal of Hazardous Materials

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“…Thus, the effectiveness of immobilized cell systems can be reduced by mass transfer limitations (Mavituna, 1986). With proper design of an immobilized cell reactor, external mass transfer resistance can be made negligible , for example, by increasing the velocity of the bulk solution relative to the gel particle (Grunwald et al, 1997). However, internal mass transfer resistance, which is affected by system design parameters such as particle size, cell loading, flow, substrate concentration and reactor type, generally is not negligible .…”

Section: Introductionmentioning

confidence: 99%

Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca‐Alginate gel beads

Engler

Lee

2007

Biotech & Bioengineering

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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) m(2)/s and 4.28 x 10(-11) m(2)/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.

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“…The effective diffusivity of substrate was calculated at the proposed conditions of the present work and according to the references [ 33 , 34 ]. The details of the method and equations are illustrated in these references.…”

Section: Resultsmentioning

confidence: 99%

Simulation of Enzyme Catalysis in Calcium Alginate Beads

Al-Mayah

2012

Enzyme Research

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A general mathematical model for a fixed bed immobilized enzyme reactor was developed to simulate the process of diffusion and reaction inside the biocatalyst particle. The modeling and simulation of starch hydrolysis using immobilized α-amylase were used as a model for this study. Corn starch hydrolysis was carried out at a constant pH of 5.5 and temperature of 50°C. The substrate flow rate was ranging from 0.2 to 5.0 mL/min, substrate initial concentrations 1 to 100 g/L. α-amylase was immobilized on to calcium alginate hydrogel beads of 2 mm average diameter. In this work Michaelis-Menten kinetics have been considered. The effect of substrate flow rate (i.e., residence time) and initial concentration on intraparticle diffusion have been taken into consideration. The performance of the system is found to be affected by the substrate flow rate and initial concentrations. The reaction is controlled by the reaction rate. The model equation was a nonlinear second order differential equation simulated based on the experimental data for steady state condition. The simulation was achieved numerically using FINITE ELEMENTS in MATLAB software package. The simulated results give satisfactory results for substrate and product concentration profiles within the biocatalyst bead.

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The determination of effective diffusion coefficients in a polysaccharide matrix used for the immobilization of biocatalysts

Cited by 24 publications

References 0 publications

Impact of substrates and cell immobilization on siderophore activity by Pseudomonads in a Fe and/or Cr, Hg, Pb containing-medium

Impact of substrates and cell immobilization on siderophore activity by Pseudomonads in a Fe and/or Cr, Hg, Pb containing-medium

Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca‐Alginate gel beads

Simulation of Enzyme Catalysis in Calcium Alginate Beads

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