Perspectives on ecological risks of microplastics and phthalate acid esters in crop production systems

Microplastics(MPs)and phthalate acid esters(PAEs)co-occur as emerging contaminants of global importance.Their abundance in soil is of increasing concern as plastic-intensive practices continue.Mulching with plastic films,inclusion in fertilizers,composts,sludge application,and wastewater irrigation are all major and common sources of MPs and PAEs in soil.Here,we review studies on the concentration and effects of MPs and PAEs in soil.While there is limited research on the interactions between MPs and PAEs in agroecosystems,there is evidence to suggest they could mutually affect soil ecology and plant growth.Therefore,we propose new research into 1)establishing an efficient,accurate,and simple method to quantify different types of microplastics in soils and plants;2)exploring the behavior and understanding the mechanisms of co-transfer,transformation,and interactions with soil biota(especially in vegetable production systems);3)assessing the risk and consequences of combined and discreet impacts of MPs and PAEs on plants and soil biota,and 4)preventing or reducing the transfer of MPs and PAEs into-and within-the food chain.

Modification of PAE-degrading Esterase(CarEW)for Higher Degradation Efficiency Through Integrated Homology Modeling,Molecular Docking,and Molecular Dynamics Simulation

Six phthalate acid esters(PAEs)priority pollutants[dimethyl phthalate(DMP),diethyl phthalate(DEP),dibutyl phthalate(DBP or DNBP),di-n-octyl phthalate(DNOP),di 2-ethyl hexyl phthalate(DEHP),and butyl benzyl phthalate(BBP)]were opted as the research object.PAE-degrading esterase CarEW(PDB ID:1C7I)isolated from Bacillus subtilis acting as a template and an iterative saturation mutation strategy was adopted to modify key amino acids to attain efficient PAE-degrading esterase substitutes with a reasonable structure constructed by homology modeling method.Present study designed a total of 285 unit-site and multi-site substitutions of PAE-degrading esterase using the homology modeling method.Among them,207 PAE-degrading esterase substitutions,which contained the 6-site PAE-degrading esterase substitute 1C7I-6-9 with 84.21%enhancement intensity of degradation ability revealed better degradability to all the 6 PAEs after modification.Moreover,molecular dynamics simulation based on the Taguchi method reported the optimal external application environment for PAE-degrading esterase substitutes as follows:pH=6,T=35℃,the rhamnolipid concentration was 50 mg/L,the molar ratio of nitrogen to phosphorus(N:P)was 10:1,the concentration of H2O_(2) was 50 mg/L,and the voltage gradient was 1.5 V/cm.The degradation ability of PAE-degrading esterase substitutes was found to be elevated by 13.04%as compared to that of the blank control under the optimal condition.Moreover,11 highly efficient PAE-degrading esterase substitutes with thermal stability were designed.