Improvement of plasmid stability by immobilization of recombinant microorganisms

Use and engineering aspects of immobilized cells in biotechnology

A short review of the research in the past two years (1990-1991) on immobilized whole cells, such as microbial, plant, and animal cells, is presented including a discussion from an engineering point of view. Recent works concerning the intraparticle mass transfer effect on immobilized microbial cells by the authors and their co-workers are also introduced. Finally, future prospects of the immobilized cell system will be discussed.

Improvement of plasmid stability of recombinant Bacillus-subtilis cells in continuous immobilized cultures

The immobilization of recombinant Bacillus subtilis in K-carrageenan gel beads has been performed in order to study the growth conditions inside the gel beads and to improve plasmid stability. Bacterial colonies showing high cell density were studied using scanning electron microscopy. A series of continuous cultures of free and immobilized B. subtilis MT119 (pHV1431, pIL252 and pIL252 Kpn) have been developed without selection pressure. In the free-cell systems, it was found that a loss of plasmid vectors occurred after a short period. In contrast, in the immobilized cell systems, plasmid-free segregants were not detected in any of the cases during the first 80 h of the culture.