Abstract
To achieve one-step separation of heavy metal ions from contaminated water, we have developed a novel bioremediation technology based on self-immobilization of the Caulobacter crescentus recombinant strain JS4022/p723-6H, which overexpresses hexahistidine peptide on the surface of the bacterial cells and serves as a whole-cell adsorbent for dissolved heavy metals. Biofilms formed by JS4022/p723-6H are effective at retaining cadmium from bacterial growth media or environmental water samples. Here we provide additional experiment data discussing the application potential of this new technology. Supplementation of calcium to the growth media produced robust JS4022/p723-6H cells by alleviating their sensitivity to chelators. After growth in the presence of 0.3% CaCl(2)·2H(2)O, double the amount of JS4022/p723-6H cells survived the treatment with 2 mM EDTA. Free cells of JS4022/p723-6H effectively sequestered 51% of the total cadmium from a Lake Erie water sample at pH 5.4, compared to 37% retrieved by the control strain. Similar levels of adsorption were observed at pH 4.2 as well. Cells of JS4022/p723-6H were tolerant of acid treatment for 90 min at pH ≥1.1 or 120 min at pH ≥2.5, which provides an avenue for the convenient regeneration of the bacterial cells metal-binding capacity with acidic solutions. Designs of possible bioreactors and an operation system are also presented.