氯代乙烯的厌氧微生物还原脱氯特性

Characterization of Reductive Dechlorination of Chlorinated Ethylenes by Anaerobic Consortium

四氯乙烯(PCE)和三氯乙烯(TCE)是地下水中典型的卤代有机化合物,严重威胁生态环境与人体健康.为获得氯代乙烯高效厌氧降解菌剂并探究其在污染地下水中的应用潜能,利用某工业污染场地的地下水,通过投喂PCE或TCE进行长期富集培养,获得了可将PCE和TCE完全脱氯成无毒乙烯的厌氧菌剂W-1.菌剂W-1的PCE和TCE脱氯速率分别是(120.1±4.9)μmol·(L·d)^(-1)和(172.4±21.8)μmol·(L·d)^(-1).16S rRNA基因扩增子测序和qPCR结果表明,98.3μmol PCE还原脱氯至顺-1,2-二氯乙烯(cis-1,2-DCE)时,Dehalobacter丰度从1.9%增长至57.1%,基因拷贝数每释放1μmol Cl-增加1.7×10^(7)copies;cis-1,2-DCE完全还原脱氯至乙烯时,Dehalococcoides丰度从1.1%增长至53.8%;PCE完全还原脱氯至乙烯过程中Dehalococcoides基因拷贝数每释放1μmol Cl^(-)增加1.7×10^(8)copies.以上结果说明Dehalobacter与Dehalococcoides协同互作实现PCE完全降解解毒.当菌群W-1以TCE为电子受体时,222.8μmol TCE完全还原脱氯至乙烯时候,Dehalococcoides丰度从(29.1±2.4)%增长至(77.7±0.2)%,基因拷贝数每释放1μmol Cl-增加(1.9±0.4)×10^(8)copies.结合PCR和Sanger测序,获得了菌剂W-1中主要脱卤菌Dehalococcoides LWT1较完整的16S rRNA基因序列,其与D.mccartyi strain 19516S rRNA基因序列相似度达100%.将菌群W-1添加至受TCE(418.7μmol·L^(-1))污染的地下水中,28 d内实现了(69.2±9.8)%的TCE被完全脱毒至乙烯,TCE脱氯速率为(10.3±1.5)μmol·(L·d)^(-1).研究成果可为PCE或TCE污染地下水开展厌氧微生物修复提供菌剂资源和理论指导.

Tetrachloroethylene(PCE)and trichloroethylene(TCE)are typical volatile halogenated organic compounds in groundwater that pose serious threats to the ecological environment and human health.To obtain an anaerobic microbial consortium capable of efficiently dechlorinating PCE and TCE to a non-toxic end product and to explore its potential in treating contaminated groundwater,an anaerobic microbial consortium W-1 that completely dechlorinated PCE and TCE to ethylene was obtained by repeatedly feeding PCE or TCE into the contaminated groundwater collected from an industrial site.The dechlorination rates of PCE and TCE were(120.1±4.9)μmol·(L·d)^(-1) and(172.4±21.8)μmol·(L·d)^(-1) in W-1,respectively.16S rRNA gene amplicon sequencing and quantitative PCR(qPCR)showed that the relative abundance of Dehalobacter increased from 1.9% to 57.1%,with the gene copy number increasing by 1.7×10^(7) copies per 1μmol Cl-released when 98.3μmol of PCE was dechlorinated to cis-1,2-dichloroethylene(cis-1,2-DCE).The relative abundance of Dehalococcoides increased from 1.1% to 53.8%when cis-1,2-DCE was reductively dechlorinated to ethylene.The growth yield of Dehalococcoides gene copy number increased by 1.7×10^(8) copies per 1μmol Cl-released for the complete reductive dechlorination of PCE to ethylene.The results indicated that Dehalobacter and Dehalococcoides cooperated to completely detoxify PCE.When TCE was used as the only electron acceptor,the relative abundance of Dehalococcoides increased from(29.1±2.4)% to(7.7±0.2)%,and gene copy number increased by(1.9±0.4)×10^(8) copies per 1μmol Cl^(-)released,after dechlorinating 222.8μmol of TCE to ethylene.The 16S rRNA gene sequence of Dehalococcoides LWT1,the main functional dehalogenating bacterium in enrichment culture W-1,was obtained using PCR and Sanger sequencing,and it showed 100%similarity with the 16S rRNA gene sequence of D.mccartyi strain 195.The anaerobic microbial consortium W-1 was also bioaugmented into the groundwater contaminated by TCE at a concentration of 418.7μmol·L^(-1).The results showed that(69.2±9.8)% of TCE could be completely detoxified to ethylene within 28 days with a dechlorination rate of(10.3±1.5)μmol·(L·d)^(-1).This study can provide the microbial resource and theoretical guidance for the anaerobic microbial remediation in PCE or TCE-contaminated groundwater.