The high level of biocatalysts such as microbial cells and enzymes plays an important role in increasing the productivity of a bioreactor. The beads entrapped with microbial cells are not strong enough for long-term use. The small void space of polymer matrix and the leakage of cells limit a final cell loading in the beads. The recent success of encapsulating microbial cells makes it possible to prepare dense biocatalyst composed of recombinant microbial cells. In addition to encapsulating microbial cells, immobilization of animal and plant cells in capsules is also briefly described.