title: Large-scale production of kappa-carrageenan droplets for gel-bead production: theoretical and practical limitations of size and production rate.
abstract: Immobilization of biocatalysts in kappa-carrageenan gel beads is a widely used technique nowadays. Several methods are used to produce the gel beads. The gel-bead production rate is usually sufficient to make the relatively small quantities needed for bench-scale experiments. The droplet diameter can, within limits, be adjusted to the desired size, but it is difficult to predict because of the non-Newtonian fluid behavior of the kappa-carrageenan solution. Here we present the further scale-up of the extrusion technique with the theory to predict the droplet diameters for non-Newtonian fluids. The emphasis is on the droplet formation, which is the rate-limiting step in this extrusion technique. Uniform droplets were formed by breaking up a capillary jet with a sinusoidal signal of a vibration exciter. At the maximum production rate of 27.6 dm3/h, uniform droplets with a diameter of (2.1 +/- 0.12) x 10(-3) m were obtained. This maximum flow rate was limited by the power transfer of the vibration exciter to the liquid flow. It was possible to get a good prediction of the droplet diameter by estimating the local viscosity from shear-rate calculations and an experimental relation between the shear rate and viscosity. In this way the theory of Newtonian fluids could be used for the non-Newtonian kappa-carrageenan solution. The calculated optimal break-up frequencies and droplet sizes were in good agreement with those found in the experiments.
authors.affiliation: Department of Food Science, Wageningen Agricultural University, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: Hunik
authors.forename: J
authors.initials: J
authors.lastname: Tramper
mesh_terms: D001709:Biotechnology / Q000379:methods; D002351:Carrageenan / Q000096:biosynthesis*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004463:Ecology; D005782:Gels; D014783:Viscosity
chemical_list: D005782:Gels; D002351:Carrageenan