biocatalysts such as microbial cells are immobilized by forming spherical gel beads containing the microbial cells from a hydrogel such as agar or carrageenan , incubating the beads for a time sufficient to permit the microbial cells to produce co 2 and thereby decrease resistance of the beads to diffusion , diffusing into the beads a monomer , cross - linking agent and accelerator and contacting the beads with a polyermization initiator to cause polymerization of the monomer . the polymerized monomer prevents breakup characteristic of hydrogels containing growing microbial cells . this method is particularly suitable for the immobilization of microbial cells for use in fermentation to produce ethanol .