Genetic surface-display of methyl parathion hydrolase on Yarrowia lipolytica for removal of methyl parathion in water.

In this study, the mph gene encoding methyl parathion hydrolase from Pseudomonas sp. WBC-3 was expressed in Yarrowia lipolytica and the expressed methyl parathion hydrolase was displayed on cell surface of Y. lipolytica. The activity of methyl parathion hydrolase displayed on the yeast cells of the transformant Z51 was 59.5 U mg⁻¹ of cell dry cells (450.6 U per mL of the culture) in the presence of 5.0 mM of Co²⁺. The displayed methyl parathion hydrolase had the optimal pH of 9.5 and the optimal temperature of 40 °C, respectively and was stable in the pH range of 4.5-11 and up to 40 °C. The displayed methyl parathion hydrolase was also stimulated by Co²⁺, Cu²⁺, Ni²⁺ and Mn²⁺, and was not affected by Fe²⁺, Fe³⁺, Na⁺, K⁺, Ca²⁺ and Zn²⁺, but was inhibited by other cations tested. Under the optimal conditions (OD(600 nm) = 2.6, the substrate concentration = 100 mg L⁻¹ and 40 °C), 90.8 % of methyl parathion was hydrolyzed within 30 min. Under the similar conditions, 98.7, 97.0, 96.5 and 94.4 % of methyl parathion in tap water (pH 9.5), tap water (pH 6.8), seawater (pH 9.5) and natural seawater (pH 8.2) were hydrolyzed, respectively, suggesting that the methyl parathion hydrolase displayed on the yeast cells can effectively remove methyl parathion in water.