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Restricted economic conditions and limited sewage treatment facilities in rural areas lead to the discharge of small-scale breeding wastewater containing higher values of residual beta-lactam antibiotics (β-lactams), which seriously threatens the aquatic environment. In this paper, molecular docking and a comprehensive method were performed to quantify and fit the source modification for the combined biodegradation of β-lactams. Using penicillin (PNC) as the target molecule, combined with contour maps for substitute modification, a three-dimensional quantitative structure–activity relationship (3D-QSAR) model was constructed for the high-performance combined biodegradation of β-lactams. The selected candidate with better environmental friendliness, functionality, and high performance was screened. By using the homology modeling algorithms, the mutant penicillin-binding proteins (PBPs) of Escherichia coli were constructed to have antibacterial resistance against β-lactams. The molecular docking was applied to obtain the target substitute by analyzing the degree of antibacterial resistance of β-lactam substitute. The combined biodegradation of β-lactams and substitute in the constructed wetland (CW) by different wetland plant root secretions was studied using molecular dynamics simulations. The result showed a 49.28% higher biodegradation of the substitutes than PNC when the combined wetland plant species of Eichhornia crassipes, Phragmites australis, and Canna indica L. were employed. [ABSTRACT FROM AUTHOR]

Methods of the root-mean-square normalization and the coefficient of variation weighting were employed to normalize and weight the biodegradation effect values of aerobic bacteria and fungi of FQs molecules, and then the comprehensive biodegradation effect 3D-QSAR model of FQs was constructed using the comprehensive biodegradation effect value as target function. It was obtained from the three-dimensional equipotential map of the constructed 3D-QSAR model, the substitution sites and substitution groups that affect the comprehensive biodegradability of FQs were screened, and the widely used levofloxacin (named FQ-16) as target molecule was selected and modified with total of 67 FQ-16 derivatives designed. It was also found that there were 5 kinds of FQ-16 derivatives' aerobic bacteria and fungi biodegradability ratio, which were predicted using FQs' aerobic bacteria and fungi biodegradability 3D QSARs, approaching to the weight ratio set by the coefficient of variation method (55.47:44.53), indicating the comprehensive biodegradation effect 3D-QSAR model of FQs effectively covering both aerobic bacteria and fungi biodegradation information, and three of above FQ-16 derivatives also passed through the functionality and photodegradability assessment with significantly improvement. Change rate in energy barrier of FQ-16 biodegradation before and after modification agreed well with the increase in their comprehensive biodegradation effect values, meaning that the designed FQ-16 derivatives' biodegradation was confirmed by biodegradation pathway simulation. This article aims to provide a theoretical method for constructing FQs molecular multi-effect 3D-QSAR model and its environment-friendly molecular modification. [ABSTRACT FROM AUTHOR]