Theoretical Design of Biodegradable Phthalic Acid Ester Derivatives in Marine and Freshwater Environments

Abstract

The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP-COOH, DBP-CHO, DBP-OH, DINP-NH₂, and DINP-NO₂) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP-OH can generate ^.OH and provides free radicals for the photodegradation of microplastics in the environment.

Keywords: microplastics; molecular modification; pharmacophore models; photodegradation; ratio normalization method.

Figure 1

A 3D congruent map of Hypo C1 and DBP, DEHP, and DINP.

Figure 2

Schematic diagrams of the substitution positions affecting the comprehensive biodegradation effect values of DBP, DEHP, and DINP.

Figure 3

Schematic diagram of the UV photodegradation pathway simulation of DBP (a) and DBP‐OH (b).

Figure 4

Schematic diagram of the aerobic biodegradation pathway simulation of DBP‐CHO (A: biodegradation pathway by Gram‐negative bacteria, B: biodegradation pathway by Gram‐positive bacteria, I. DBP‐CHO, II. phthalate monoesters, III. phthalic acid, IV. cis‐3,4‐ dihydroxy −3,4‐ dihydrogen p‐phenyl sulfonic acid; V. 3,4‐dihydroxy phthalic acid, VI. cis‐4,5‐dihydroxy‐4,5‐dihydrophthalic acid, VII. 4,5‐ dihydroxy phthalic acid, VIII. protocatechuate).

Figure 5

Schematic diagram of the biodegradability evaluation of PAE derivative molecules in various environments.