A new method for microbial cell immobilization

Immobilization of microbial cells is an important strategy to reduce the production costs of bioprocesses through simplifying the process operations, enabling repetitive or continuous use of expensive biocatalysts, for example. However, conventional immobilization via gel entrapment and chemical bonding are associated with efficiency-related problems, such as mass transfer limitation in a polymer gel, leakage of cells from a support matrix, fragility of support materials, and adverse effects of cross-linking reagents on catalytic activity. Ishikawa, Shigemori, and Hori developed a novel immobilization method which overcomes these drawbacks by utilizing a bacterionanofiber protein, which they previously identified as a new adhesin. The authors introduced the adhesin-encoding gene into a dye-producing bacterium, immobilized the transformant cells onto a polyurethane support, and demonstrated the usefulness of the new method for a chemical conversion; the immobilization enhanced cell tolerance to the toxic substrate and greatly improved the production rate and productivity compared with suspension culture.