the present invention relates to a method for immobilising microorganisms , a related material , and the use thereof in fermentation or bioconversion . specifically , the present invention relates to the immobilisation of microorganisms in optionally dehydrated polymeric spheres consisting of two or more layers . the technical problem is that only part of the total microorganism population , namely the microorganisms adjacent to the edge of the sphere , is actually active in conventional spheres . according to the present invention , this problem is solved by providing a nutrient supply in the center of the sphere and placing the microorganisms in a layer adjacent thereto , the resulting combination optionally being coated with a sterile layer defining , in this embodiment , a triple - layer sphere .