Functional cell surface displaying of acetylcholinesterase for spectrophotometric sensing organophosphate pesticide

The inhibition of acetylcholinesterase (AChE) activity based methods have been widely used for rapid detection of organophosphate (OP) pesticide residues. However, the sensitivity of the enzyme toward pesticides is not desirable and complex purification steps increase production cost. In this study, we optimized and synthesized the cDNA of carp AChE based on the preferred codon using Saccharomyces cerevisiae, which was ligated into expression vector pYD1. The AChE was successfully presented on yeast surface through a-agglutinin mediated display system. In shake-flask after induction with galactose in YPD medium for 24 h, this strain expressed AChE activity at a high level of 0.15 U/OD600/ml. The correct location of AChE was confirmed by immunofluorescence analysis. The whole cell catalyst was applied to visible spectrophotometry detection for OP pesticides based on inhibition rate. The inhibition rate was linear with paraoxon concentration in the range of 0.5 ng/ml-10 mu g/ml and parathion concentration in the range of 5 ng/ml-10 mu g/ml. The low detection limit was 0.136 ng/ml paraoxon and 3.72 ng/ml parathion (S/N = 3). The proposed method is applicable to analyzing OP pesticides in real samples. Therefore, the recombinant strain developed could be an efficient and affordable biomaterial for rapid and accurate detection of OP pesticide residues.