Diffusion in cell-free and cell immobilising kappa-carrageenan gel beads with and without chemical reaction

Diffusion into and from K-carrageenan gel beads was studied, both in the ab sence and presence of bacterial cells, both with and without biochemical re action. The solutes were indole, L-serine, and L-tryptophan. The reaction w as that of indole and L-serine to give L-tryptophan. Established theory con cerning diffusion of a single solute in cell-free gels was found to describ e well the effect of the gel on diffusivity. Simultaneous diffusion of the three solutes resulted in lower diffusivities than those for individual sol utes, suggesting the need to use multicomponent diffusion theory. The effec t of cells on diffusion could only be accounted for by models assuming perm eable cells. Diffusion with chemical reaction was reasonably well described by an effectiveness factor calculated using an effective diffusivity estim ated from diffusion data without reaction. (C) 1999 John Wiley & Sons, Inc.