Highly selective preconcentration of ultra-trace cadmium by yeast surface engineering

• Published in: Analyst (London) 2012-09, Vol.137 (18), p.4193-4199
• Main Authors: Yang, Ting, Zhang, Xiao-Xing, Chen, Ming-Li, Wang, Jian-Hua
• Format: Article
• Language: English
• Subjects: Adsorption; Analytical chemistry; Applied sciences; Cadmium - analysis; Cadmium - chemistry; Cells, Immobilized; Chemistry; Exact sciences and technology; Global environmental pollution; Pollution; Saccharomyces cerevisiae; Spectrometric and optical methods; Spectrophotometry, Atomic - methods; Surface Properties; Trace Elements - analysis; Trace Elements - chemistry
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c2an35755k

The potential of selective cell-sorption for separation/preconcentration of ultra-trace heavy metals was exploited by surface engineering of Saccharomyces cerevisiae cells. The general idea is to display the cadmium-binding peptide on the cell surface in order to enhance the covalent interaction between cadmium and the yeast cells. By immobilizing the surface-engineered yeast cells onto cytopore ® microcarrier beads for cadmium adsorption, we demonstrated that with respect to the native yeast 600-fold and 25-1000-fold improvements were observed respectively for the tolerance of ionic strength and the tolerant capability toward various metal cations after surface engineering. Based on these observations, a novel procedure for selective cadmium preconcentration was developed with detection by graphite furnace atomic absorption spectrometry (GFAAS), employing the engineered S. cerevisiae cell-loaded cytopore ® beads as a renewable sorption medium incorporated into a sequential injection lab-on-valve system. The cadmium retained on the yeast cell surface was eluted with a small amount of nitric acid and quantified with GFAAS. Within a range of 5-100 ng L 1 and a sample volume of 1 mL, an enrichment factor of 30 was achieved along with a detection limit of 1.1 ng L 1 , a sampling frequency of 20 h 1 and a precision of 3.3% RSD at 50 ng L 1 . The procedure was validated by analyzing cadmium in certified reference materials and a series of environmental water samples. The display of cadmium-binding peptide on the surface of Saccharomyces cerevisiae cell significantly enhances the tolerance of ionic strength and tolerant capability toward coexisting metal cations.