全氟辛烷磺酰胺降解菌的分离、鉴定和降解特性

Isolation, identification, and degradation characteristics of perfluorooctane sulfonamide-degrading bacterium

摘要:

【背景】全氟烷基和多氟烷基物质(per-and poly-fluoroalkyl substances, PFAS)是一类具有高表面活性、热稳定性、化学稳定性和疏水疏油性的难降解有机污染物。其长距离迁移性、极高的环境持久性和生物蓄积性给生态环境和生物体带来了严重的危害。【目的】从吉林石化公司污水处理厂水样中筛选获得以全氟辛烷磺酰胺(perfluorooctane sulfonamide, PFOSA)为唯一碳源生长的降解菌，并分析其降解特性及机理。【方法】以PFOSA为唯一碳源，通过富集、筛选、分离和纯化，从污水中筛选出PFOSA好氧降解菌，通过形态学观察、16S rRNA基因和全基因组测序分析对菌株进行鉴定，并采用三重四级杆液质联用仪分别对PFOSA的降解率和降解产物进行分析。【结果】筛选得到一株PFOSA好氧降解细菌C11，经形态学观察、16S rRNA基因序列分析和全基因组测序分析，初步鉴定该菌为睾丸酮丛毛单胞菌(Comamonas testosteroni)。经单因素优化试验发现，在培养温度为30 ℃、初始pH值为7.0、PFOSA初始浓度为30 mg/L的降解条件下，菌株C11对PFOSA的降解率可达64.6%，PFOSA的降解产物为全氟辛烷磺酸(perfluorooctane sulfonate, PFOS)、全氟辛酸(perfluorooctanoic acid, PFOA)、全氟庚酸(perfluorodecanoic acid, PFHpA)和全氟己酸(perfluorohexanoic acid, PFHxA)，基于降解产物的初步推定，在菌株C11的作用下对降解途径进行推测：首先PFOSA脱去氨基转化为PFOS，PFOS脱去磺酸基团氧化成PFOA，最后C-F键发生断裂转化为PFHpA和PFHxA。【结论】菌株C11对PFOSA具有很好的降解能力，为进一步解析PFOSA生物降解机理和探索PFAS污染环境的生物修复路径提供了理论支持。

Abstract:

[Background] Per-and poly-fluoroalkyl substances (PFAS), a class of organic pollutants with high surface activity, thermal stability, chemical stability, hydrophobicity, and lipophobicity, are difficult to be degraded. Due to the long-distance migration, strong environmental persistence, and bioaccumulation, PFAS has brought serious harm to the environment and organisms. [Objective] To isolate an efficient perfluorooctane sulfonamide (PFOSA)-degrading bacterium from a sewage treatment plant and analyze the degradation characteristics and mechanism. [Methods] An aerobic PFOSA-degrading bacterium was screened out from wastewater by enrichment, isolation, and purification with PFOSA as the sole carbon source. The strain was identified by morphological observation and 16S rRNA gene and whole-genome sequencing. The degradation rate and degradation products of PFOSA were analyzed by a triple quadrupole mass spectrometer. [Results] An aerobic PFOSA-degrading bacterium C11 was isolated and identified as Comamonas testosteroni. The single factor experiments for degradation condition optimization showed that the degradation rate of PFOSA by strain C11 reached 64.6% under the optimal conditions of 30 ℃, pH 7.0, and PFOSA concentration of 30 mg/L. The degradation products of PFOSA were perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFHpA), and perfluorohexanoic acid (PFHxA). According to the degradation products, we preliminarily hypothesized the degradation pathway of strain C11. Specifically, PFOS generated from the deamination of PFOSA was desulfonated and oxidized to PFOA, which was then converted into PFHpA and PFHxA after the cleavage of C–F bond. [Conclusion] Strain C11 has a strong ability of degrading PFOSA, which provides theoretical support for deciphering the biodegradation mechanism of PFOSA and exploring the bioremediation path of PFAS-contaminated environment.