Abstract

Enantioselective biodegradation of racemic dichlorprop in two soils was investigated in the laboratory. Chiral separation of racemic dichlorprop was achieved by using HPLC with Phenomenex Lux Amylose-2. The first-order kinetic model fitted well the dissipation data of racemic dichlorprop and its pure R- and S-enantiomers. S-dichlorprop was preferentially degraded in both soils and enantioselectivity was affected by soil pH. The half-lives (DT₅₀) of S-dichlorprop were 8.22 days in soil A and 8.06 days in soil D, while R-dichlorprop was more persistent with DT₅₀ of 12.93 days in soil A and 12.38 days in soil D, respectively. Dichlorprop dissipated faster in soil D with lower organic matter content. In sterilized soils, neglected dissipation was observed and enantiomer fraction values remained constant, indicating that the enantioselective degradation was mainly controlled by soil microorganisms. Soil microbial community structure and diversity was assessed by Illumina MiSeq sequencing of 16S rRNA genes from dichlorprop and no dichlorprop contaminated microcosms. Compared with controls, dichlorprop application had no significant effect on microbial community structures at phylum level, but increased bacterial diversity and dichlorprop degradation related taxa in both soils. S-dichlorprop preferential degradation might be attributed to the S-enantiomer preferred degraders in the family of Sphingomonadaceae.

摘要

在实验室中研究了两种土壤中外消旋敌敌畏的对映选择性生物降解。外消旋二氯丙酸酯的手性分离是通过使用Phenomenex Lux Amylose-2进行的HPLC实现的。一阶动力学模型很好地拟合了外消旋二氯丙醇及其纯R-和S-对映异构体的耗散数据。S-二氯丙醇在两种土壤中均优先降解，对映选择性受土壤pH值的影响。S-二氯丙醇在土壤A中的半衰期（DT ₅₀）为8.22天，在D中为8.06天，而R-二氯丙醇在DT _50中更持久分别在土壤A中的12.93天和在土壤D中的12.38天。敌敌畏在有机质含量较低的土壤D中的消散速度更快。在无菌土壤中，观察到的耗散被忽略，对映体分数值保持恒定，表明对映选择性降解主要由土壤微生物控制。土壤微生物群落结构和多样性通过Illumina MiSeq测序，评估了双氯丙酸和没有被双氯丙酸污染的微观世界中的16S rRNA基因。与对照组相比，敌敌畏在门类水平上对微生物群落结构没有显着影响，但两种土壤中细菌多样性和敌敌畏降解相关类群均增加。S-二氯丙醇的优先降解可能归因于S-对映异构体优先的降解体鞘翅目科。