Title

Self-immobilization of recombinant Caulobacter crescentus and its application in removal of cadmium from water

Document Type

Article

Publication Date

10-1-2010

Publication Title

Applied Biochemistry and Biotechnology

Volume

162

Issue

4

First Page

1160

Keywords

Biofilm, Bioremediation, Cadmium, Caulobacter crescentus, Heavy metals, Immobilization, S-layer

Last Page

1173

Abstract

Microbial biofilms can be valuable in many biotechnological applications, including bioremediation. We have previously constructed a recombinant strain of Caulobacter crescentus JS4022/p723-6H by inserting a hexahistidine peptide to a permissive site of the host surface layer (S-layer) protein RsaA. This engineered strain is highly effective in removal of cadmium from water as free cells. In this communication, we examined the biofilms formed by self-immobilized JS4022/p723-6H and evaluated their ability to retrieve cadmium from contaminated water samples. According to light and electron microscopic observations, JS4022/p723-6H cells developed a uniform monolayer biofilm on borosilicate surfaces through their intrinsic appendage, a stalk with an adhesive holdfast. The density of the biofilms reached a maximum after 48 h of incubation and was not affected by exposure to at least 1 ppm cadmium. When 0.4 ppm Cd(II) was added to the growth medium, immobilized JS4022/p723-6H removed 76.9% of the total metal, whereas the control strain only removed 13.5%. When a water sample collected from Lake Erie was spiked with various amounts of CdCl2, immobilized JS4022/p723-6H was able to sequester 44∼51% of the total metal, compared to 37∼42% accumulated by the control strain. By combining two powerful techniques, cell surface display and self-immobilization, we achieved complete separation of dissolved heavy metals from contaminated water in a single step. This study laid down the foundation to cost-effectively construct large-scale bioreactors with high efficiency and specificity to retrieve environmental contaminants from water. © 2010 Springer Science+Business Media, LLC.

DOI

10.1007/s12010-009-8885-4

ISSN

02732289

PubMed ID

20069463

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