一株全氟及多氟烷基化合物脱氟菌类诺卡氏菌NJF-4的分离及脱氟特性

Isolation and characterization of Nocardioides sp. NJF-4 capable of defluorinating PFAS

摘要:

【背景】 全氟及多氟烷基化合物(per- and poly-fluoroalkyl substances, PFAS)是一种新型持久性污染物，C−F键的高键能使得PFAS难以实现生物降解。目前已有能够生物降解单氟化合物的研究报道；而相对于单氟化合物的降解菌，已被报道的多氟或全氟烷基化合物的降解微生物纯菌株则十分有限。【目的】 从土壤中分离脱氟菌，研究其对单氟和多氟化合物的生物脱氟作用。【方法】 利用单氟化合物1-氟癸烷(1-fluorodecane, FD)为唯一碳源底物分离筛选脱氟菌株类诺卡氏菌(Nocardioides sp.) NJF-4。通过氟离子比色检测法探究菌株NJF-4对三氟化合物[4,5,5-三氟-4-戊烯酸(4,5,5-trifluoropent-4-enoic acid, TFE)]和六氟化合物[4,4,4-三氟-3-(三氟甲基)巴豆酸(4,4,4-trifluoro-3-(trifluoromethyl)crotonic acid, SFC)]的生物脱氟作用。【结果】 类诺卡氏菌NJF-4能够利用FD作为唯一碳源，在无机盐培养基(minimal medium, MM)中培养7 d后脱氟率达到(70.5±5.4)%。以多氟化合物作为碳源，在改进后无机盐培养基(MM-G)中培养28 d后TFE降解率为(42.0±2.6)%，脱氟率为(11.70±0.66)%；培养49 d后SFC降解率为(36.70±0.87)%，脱氟率为(2.57±0.15)%。共代谢降解实验发现乙酸铵能够显著提高多氟化合物的生物脱氟效果，TFE脱氟效率达到(21.2±1.9)%，脱氟效果提高了1.8倍；SFC脱氟率为(9.61±0.72)%，脱氟效果提高了3.7倍。共代谢条件下TFE降解效率没有显著提升，而SFC降解率有所提高，该条件下2种多氟化合物的相对脱氟率均显著提升。【结论】 菌株NJF-4不仅对单氟烷烃具有脱氟能力，同时也能对多氟化合物进行生物脱氟，共代谢降解可以有效促进多氟化合物的生物脱氟效果；脱氟菌株的筛选也为系统开展生物脱氟机制奠定了研究基础。

Abstract:

[Background] Per- and polyfluoroalkyl substances (PFAS) are emerging persistent pollutants recalcitrant to biodegradation due to the strong C−F bonds. While biodefluorination of mono-fluorinated compounds has been reported, studies on the biodefluorination of polyfluoroalkyl substances, specifically by pure cultures, remain limited. [Objective] To isolate bacteria that can defluorinate mono-fluorinated substances and assess their capability of defluorinating PFAS. [Methods] A defluorinating strain, Nocardioides sp. NJF-4, was isolated with 1-fluorodecane (FD) as the sole carbon source. Colorimetric detection of fluoride was employed to evaluate the defluorinating effects of NJF-4 on the tri-fluorinated compound 4,5,5-trifluoropent-4-enoic acid (TFE) and the hexa-fluorinated compound 4,4,4-trifluoro- 3-(trifluoromethyl)crotonic acid (SFC). [Results] NJF-4 effectively utilized FD as the sole carbon source, with a defluorination rate of (70.5±5.4)% after 7 days of incubation in the minimal medium (MM) with FD. With TFE as the carbon source in the MM-G medium, NJF-4 exhibited a degradation rate of (42.0±2.6)% and a defluorination rate of (11.70±0.66)% on day 28. With SFC as the carbon source in the MM-G medium, NJF-4 exhibited a degradation rate of (36.70±0.87)% and a defluorination rate of (2.57±0.15)% on day 49. The addition of ammonium acetate significantly improved the biodefluorination of poly-fluorinated compounds. Under cometabolic conditions, the defluorination efficiency on TFE reached (21.2±1.9)%, a 1.8-fold increase compared with that in the absence of ammonium acetate, while the defluorination efficiency on SFC was (9.61±0.72)%, representing a 3.7-fold increase. Under cometabolic conditions, the degradation of TFE showed no significant increase, whereas that of SFC was significantly enhanced. The relative defluorination efficiency was significantly improved following the addition of ammonium acetate. [Conclusion] NJF-4 capable of defluorinating mono-fluorinated compounds can also defluorinate poly-fluorinated compounds. The biodefluorination of PFAS was significantly stimulated under cometabolic conditions. The isolation of defluorinating bacteria provides a foundation for exploring the mechanisms underlying biodefluorination.