title: Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca-alginate gel beads.
abstract: 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.
authors: Samsung Engineering Co. Ltd., R&D Center, Seoul, Republic of Korea.
authors: Jiyeon
authors: J
authors: Ha
authors: Cady R
authors: CR
authors: Engler
authors: Seung Jae
authors: SJ
authors: Lee
mesh_terms: D000464:Alginates / Q000737:chemistry*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D048429:Cell Size; D018914:Cells, Immobilized; D004058:Diffusion; D004926:Escherichia coli / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D005782:Gels / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D007700:Kinetics; D008863:Microspheres; D008956:Models, Chemical; D063086:Organothiophosphates / Q000737:chemistry* / Q000378:metabolism; D010316:Particle Size; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics; D015202:Protein Engineering; D012212:Rheology; D014468:Umbelliferones / Q000737:chemistry* / Q000378:metabolism; D014783:Viscosity
chemical_list: D000464:Alginates; D005782:Gels; D006603:Hexuronic Acids; D063086:Organothiophosphates; D014468:Umbelliferones; C041609:O,O-diethyl phosphorothionate; D020723:Glucuronic Acid; C045290:phosphorylphosphatase; D010744:Phosphoric Monoester Hydrolases; C305311:chlorferron