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 enhancemetal adsorption to microbial cells. The transcription factor CadR of Pseudomonasputida shows highly selective affinity with Cd2+. 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 Cd2+ adsorption capacity of yeast cells. The surface-engineered cells also performed well at mesophilic and higher temperatures (30-50 degrees C) under neutral or alkalescent conditions. With an initial concentration of 1.0 mg L-1, the Cd2+ 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 Cd2+ in the presence of Zn2+ and Pb2+. 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 Cd2+. (C) 2015 Society of Chemical Industry