Physical properties and heavy metal uptake of encapsulated Escherichia coli expressing a metal binding gene (NCP)

Abstract

A recombinant Escherichia coli expressing the Neurospora crassa metallothionein gene (NCP) has previously been shown to remove low levels of Cd and other metals from solution. For further development as a biosorbent, the encapsulation of the NCP is investigated by various matrices. The NCP was encapsulated in alginate, chitosan-alginate or kappa -carrageenan, and its physical properties characterized. Results indicated that encapsulation in alginate resulted in fragile beads, whereas encapsulation in kappa -carrageenan or chitosanalginate provided more physical and chemical integrity to the beads. Maximal heavy metal removal by cells encapsulated in carrageenan occurred within 3h, while a gradual increase in removal was observed up to 24h for cells encapsulated in chitosan-alginate. Metal removal by cells encapsulated in alginate beads was lower than those encapsulated in carrageenan or chitosanalginate.

Keywords::

• Encapsulation;Beads;Alginate;Chitosan;Carrageenan;Metal;Removal