Construction of Genetically Engineered Escherichia coli Cell Factory for Enhanced Cadmium Bioaccumulation in Wastewater

Abstract

The heavy metal cadmium poses severe threats to both ecosystems and human health. Utilizing genetic engineering to enhance the microbial capability for efficient cadmium accumulation has emerged as a pivotal research direction. This study constructed a genetically engineered bacterium capable of expressing multivalent phytochelatins with a self-assembly ability and explored its efficacy in cadmium adsorption. Molecular biology techniques were adopted to fuse the recombinant human ferritin (rHF) gene and the synthetic phytochelatin (EC) gene, known for its robust adsorption capacity for heavy metals. The expression vector was constructed. Escherichia coli (E. coli) served as the host cell to express multivalent nanochelator rHF-ECs tailored for high-efficiency heavy metal adsorption. The results reveal the successful soluble expression of the recombinant fusion protein in E. coli cells, forming self-assembled multivalent nanoparticles with a size of about 13 nm, and the target protein rHF-EC20 (monomer) could adsorb approximately 9.2 μmol of Cd2+ in vitro. Moreover, this recombinant strain demonstrated cadmium adsorption across a temperature range of 16–45 °C and a pH range of 5–9, with the optimal performance observed at pH 7.0 and 37 °C. Compared with the control strain, the recombinant strain BL21 (FLE), expressing nano-chelating peptides, achieves an adsorption rate of 80% for Cd2+ at 60 min, resulting in an approximately 18% increase in the Cd2+ enrichment efficiency. The maximum adsorption capability of cadmium reached 12.62 mg per gram of dry cell weight. This work indicated that the synthesis of multivalent chelating peptides in E. coli cells could efficiently enhance the bioaccumulation of the heavy metal cadmium, which renders novel avenues and methodologies for addressing cadmium pollution, offering promising prospects for environmental remediation.