Surface‐engineered Saccharomyces cerevisiae cells displaying redesigned CadR for enhancement of adsorption of cadmium (II)

BACKGROUND The use of cell‐surface display technology to express recombinant proteins on a microbial cell surface can enhance metal adsorption to microbial cells. The transcription factor CadR of Pseudomonas putida shows highly selective affinity with Cd 2+ . RESULTS CadR was genetically engineered by truncating 47 N‐terminal amino acids and 21 C‐terminal amino acids in order to maximize its expression efficiency while maintaining its metal‐binding domain. The redesigned CadR (named T68CadR ) was then displayed with Saccharomyces cerevisiae a‐agglutinin cell‐surface display system. This engineering approach enhanced the H + / OH − buffering capacity and the Cd 2+ adsorption capacity of yeast cells. The surface‐engineered cells also performed well at mesophilic and higher temperatures (30–50 °C) under neutral or alkalescent conditions. With an initial concentration of 1.0 mg L −1 , the Cd 2+ removal efficiency remained 85% when the concentration of Na + changed from 0 to 400 mmol L −1 ( pH 7.8). The surface‐engineered cells also showed highly selective adsorption to Cd 2+ in the presence of Zn 2+ and Pb 2+ . CONCLUSIONS T68CadR displayed yeast cells constructed in this study provide an option to selectively remove Cd in water. It also might be promising as a tool to determine CadR 's Cd‐binding mechanism and to improve its selectivity and affinity to Cd 2+ .