Improving dioxygenase stability by gene chromosome insertion: implementation in immobilized-cell systems.

The immobilization of recombinant cells by using the unstable 3,4-dihydroxyphenylacetate 2,3-dioxygenase was studied as a model. Dioxygenase activity and cell viability were compared in immobilized-cell systems and cells in suspension. Immobilization increased enzyme stability and the efficient degradation of 3,4-dihydroxyphenylacetate. The stability of the cloned enzyme and the viability of the immobilized recombinant cells were well maintained for at least 15 days. We used the strain Escherichia coli CC118-D in which the hpaB gene from Klebsiella pneumoniae, coding for the subunit of 3,4-dihydroxyphenylacetate 2,3-dioxygenase, was inserted into the chromosome. This study has demonstrated that the implementation of E. coli CC118-D in a pilot-scale bioreactor resulted in a 100% stabilization of dioxygenase activity, and could be a useful tool for bioremediation processes.