Determination of glucose and ethanol effective diffusion coefficients in Ca-alginate gel.
Glucose and ethanol diffusion coefficients in 2% Ca-alginate gel were measured using the experimental technique based on solute diffusion into or out of gel beads in a well-stirred solution. The aim of the study was to make the measurements under typical conditions found in alcoholic fermentations, such as the concentrations of glucose (100 g l-1) and ethanol (50 g l-1), the simultaneous counter-diffusion of glucose and ethanol, and the presence of cells in the gel beads at a level of 10(9) cells g-1 of beads. Previously, an evaluation of the error associated with the methodology used indicated how the experimental procedure would minimize the error. The individual measurement of glucose and ethanol coefficients in 2% Ca-alginate with no cells gave values of 5.1 and 9.6 x 10(-6) cm2 s-1, respectively, which are lower than those in water. When the effect of counter-diffusion was investigated, both coefficients decreased: glucose by 14% and ethanol by 28%. When cells were incorporated into the beads, only the ethanol coefficient decreased significantly, while the glucose coefficient apparently increased its value to 6.9 10(-6) cm2 s-1.
Estapé
D
D
Unitat d'Enginyeria Química, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Gòdia
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F
Solà
C
C
D000464:Alginates; D004058:Diffusion; D000431:Ethanol / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical
D000464:Alginates; D006603:Hexuronic Acids; D000431:Ethanol; D020723:Glucuronic Acid; D005947:Glucose