Adenine deficient yeast: A fluorescent biosensor for the detection of Labile Zn(II) in aqueous solution.

Labile Zn(II) species play key roles in inducing bioresponse. Thus the development of a biosensor for labile Zn(II) quantification is important. In this study, we demonstrate that the autofluorescence intensity (FITC channel) of an adenine deficient yeast (Ade(-) yeast) was enhanced in the presence of Zn2+. Yeast cells were firstly cultured for 24 h to obtain the Ade(-) yeast, and the biomass (OD value) was optimized to be 0.03. After pre-culturing in D-glucose at 2.5 g/L for 1 h, the cells were transferred to 2.5 g/L D-glucose containing Zn2+ and the autofluorescence intensity was determined by flow cytometry after 1 h. The biosensor could detect Zn2+ at ultralow concentration (0.01 μM) in the optimized medium and accurately quantify the extracellular concentrations of Zn2+ ranging from 0.01 to 0.5 μM. High tolerance of Ade(-) yeast to salinity, pH variation and other metals enabled its application as a biosensor for labile Zn detection in complex media. Determining dissolved Zn2+ from a viscous sample (zinc cream), Ade(-) yeast accurately quantified the labile Zn2+ with a lower quantification limit than the chemosensor and higher simplicity than the conventional method (ICP-MS coupled with ultrafiltration). The study provides a novel biosensor based on an Ade(-) yeast and could be potentially used to detect labile Zn(II) species at trace levels in complex media.