Investigations of the oxygen supply in Ca-alginate beads and microcapsules loaded with Penicillium raistrickii using a microelectrode.

The oxygen supply of free, Ca-alginate entrapped and microencapsulated mycelia of Penicillium raistrickii i 477 capable of 15 alpha-hydroxylation of 13-ethyl-gon-4-en-3,17-dione was investigated. Using an oxygen microelectrode distinct gradients of oxygen within the Ca-alginate beads as well as the microcapsules were detected. Slope and width of the gradients were investigated in dependence on the kind of immobilization, the culture age and the cell density on or in the carrier as well as the different forms of the oxygen supply in the medium. So it could be shown that large parts of immobilizates, approximately 96% of the diameter of both types, were oxygen-free. In comparison with free mycelia, the lower oxygen supply of the immobilized mycelia led to a metabolic shift to fermentative catabolism.