Novel fungal organophosphorus hydrolases in acidic media: an application to apples decontamination

Organophosphorus pesticides bring significant improvements in agriculture, but their toxicity causes environmental and health negative impacts. The aim of this work was the development of robust biocatalysts to be applied in bioremediation. Four fungi were evaluated as hydrolase sources capable of degrading organophosphorus pesticides: Aspergillus niger, Fusarium sp., Penicillium chrysogenum, and Penicillium nalgiovense. The hydrolysis rates of methyl paraoxon obtained under acidic conditions were in the range of 10 to 21 mg L^-1 d^-1, which is remarkable since most similar biocatalysts are active under alkaline conditions. Penicillium chrysogenum activity was outstanding, and it was selected to prepare, characterize, and study the applications of its enzymatic extract. It was used to evaluate the bioremediation of apple surfaces at pH 2 in the presence of SDS, achieving complete methyl paraoxon degradation under proposed conditions. These results indicate that this biocatalyst could complement industrialized fruit washing processes for the elimination of organophosphorus pesticides.

Spectroscopic studies of methyl paraoxon decomposition over mesoporous Ce-doped titanias for toxic chemical filtration

The ever-constant threat of chemical warfare agents (CWA) motivates the design of materials to provide better protection to warfighters and civilians. Cerium and titanium oxide are known to react with organophosphorus compounds such Sarin and Soman. To study the decomposition of methyl paraoxon (CWA simulant) on such materials, we synthesized ordered mesoporous metal oxides (MMO) TiO₂, Ce_xTi_1-xO₂ (x = 0.005, 0.5, 0.10, 0.15) and CeO₂. We fully characterized TiO₂ and Ce-doped TiO₂ and found phase-pure oxides with cylindrical hexagonally packed pores and high surface areas (176-252 m²/g). Methyl paraoxon decomposition was tracked through UV/Vis and found Ce_0.15Ti_0.85O₂ to decompose the most methyl paraoxon, but CeO₂ to be the most reactive when normalized to surface area. The surface area normalized rate constant (k_SA) for CeO₂ was 3-4.6 times larger than that of TiO₂ and the Ce_xTi_1-xO₂ series. While TiO₂ and Ce_xTi_1-xO₂ for 0.05 ≤ x ≤ 0.10 displayed no significant differences in the kinetics, the mostly amorphous Ce_0.15Ti_0.85O₂ displayed a slight increase in reactivity. Our findings indicate that the nature of the cation, Ce⁴⁺ vs Ti⁴⁺, is less important to methyl paraoxon reactivity on these MMOs compared to other factors such as crystal structure type.

Comparison of the reactivation rates of acetylcholinesterase modified by structurally different organophosphates using novel pyridinium oximes

A novel panel of oximes were synthesized, which have displayed varying degree of reactivation ability towards different organophosphorus (OP) modified cholinesterases. In the present article, we report a comparative reactivation profile of a series of quaternary pyridinium-oximes for electric eel acetylcholinesterase (EEAChE) inhibited by the organophosphorus (OP) inhibitors methyl paraoxon (MePOX), ethyl paraoxon (POX; paraoxon) and diisopropyl fluorophosphate (DFP) that are distinguishable as dimethoxyphosphoryl, diethoxyphosphoryl and diisopropoxyphosphoryl AChE-OP-adducts. Most of the 59-oximes tested led to faster and more extensive reactivation of MePOX- and POX-inhibited EEAChE as compared to DFP-modified EEAChE. All were effective reactivators of three OP-modified EEAChE conjugates showing 18-21% reactivation for DFP-inhibited AChE and ≥45% reactivation for MePOX- and POX-inhibited EEAChE. Oximes 7 and 8 showed k_r values better than pralidoxime (1) for DFP-inhibited EEAChE. Reactivation rates determined at different inhibition times showed no significant change in k_r values during 0-90 min incubation with three OPs. However, a 34-72% decrease in k_r for MePOX and POX and > 95% decrease in k_r for DFP-inhibited EEAChE was observed after 24 h of OP-exposure (aging).