| 摘要: | 三氯乙烯(Trichloroethene, TCE)是一種工業用溶劑，也是常見的環境汙染物。一般而言，三氯乙烯被廣泛用於金屬部件的脫脂。在三氯乙烯的整治技術中，零價鐵是具有潛力的技術之一，能夠作為三氯乙烯的還原催化劑，有效促進三氯乙烯通過β-elimination 轉化成無毒的產物，移除地下水或土壤中的三氯乙烯。然而，此一化學反應的主要產物中包含了乙炔，乙炔已被證明會抑制三氯乙烯的脫氯作用。本研究即是針對乙炔對生物性修復三氯乙烯的抑制作用進行探討，藉由將脫鹵球菌(Dehalococcoides mccartyi, Dhc)與乙炔發酵菌(Pelobacter acetylenovorans SFB93)共培養的方式，將造成脫氯抑制的乙炔轉換成脫氯菌生長所需的碳源，此時乙炔則作為共生系統中唯一的碳源。同時，本研究亦利用 SFB93 之固氮酶活性，扮演此共生系統中氮源提供者的角色，使脫鹵球菌在氮源缺乏條件下亦能持續進行還原脫氯。此外，由於SFB93 為一海水分離菌株，為找出最適合的共生條件，本研究中探討了鹽度對於脫氯菌共生系統的影響，以在共生環境中取得最好的脫氯效率。在共生系統中，1.6 mM 乙炔會對 Dhc 還原脫氯造成顯著的抑制作用，且無法在SFB93 消耗乙炔後而得到恢復。然而，當乙炔濃度低於 0.1 mM 以下便不會對還原脫氯造成抑制。結合上述結果，最終本研究以 0.1 mM 乙炔作為共生系統中唯一碳源，並且調整氯化鈉濃度至 10g/L、15g/L 及 20g/L，成功建立 Dhc 與 SFB93 共培養系統，並在無添加額外氮源且僅有乙炔作為唯一碳源的之條件下，共培養系統中的脫鹵球菌能夠持續進行還原脫氯，FL2 能夠將 TCE 還原至氯乙烯(vinyl chloride, VC)並有部分乙烯產生，而 BAV1 能夠將二氯乙烯(cis-1,2-Dichloroethylene, cis-DCE)還原至無毒性乙烯。共培養系統能夠解決透過微生物間的相互作用解決實場整治上脫鹵球菌因生物可利用
性氮源缺乏而導致還原脫氯活性下降之困境，可發展有應用潛力的TCE生物整治方式。;Trichloroethylene (TCE) is an industrial solvent and a common environmental pollutant. Trichloroethylene is widely used for degreasing metal material. Zero-valent iron is one of the potential remediation technologies for trichloroethylene. It can be used as a reduction catalyst for trichloroethylene, which can effectively promote the conversion of trichloroethylene into non-toxic products through β-elimination, and remove trichloroethylene present in groundwater or soil. However, the middle product of this chemical reaction contains acetylene, which has been shown to inhibit the biological dechlorination of trichloroethylene.
The purpose of this research is to investigate the inhibitory effect of acetylene on bioremediation of trichloroethylene. We co-cultured Dehalococcoides mccartyi (Dhc) with Pelobacter acetylenovorans SFB93 by using acetylene as the sole carbon source. At the same time, we also used the nitrogenase activity of SFB93 to support the nitrogen sources in this symbiotic system, so that Dhc can perform reductive dechlorination continuously even under a nitrogen-deficient environment. As SFB93 is a seawater-isolated strain, demonstrated that the effects of salinity on this symbiotic system results revealed that 1.6 mM acetylene caused a significant inhibitory effect on the reductive dechlorination of Dhc and could not be recovered after the consumption of acetylene by SFB93. However, the reductive dechlorination was not inhibited when the acetylene concentration was below 0.1 mM. Combined with the above results, we used 0.1 mM acetylene as the sole carbon source in the coculture system with a salinity of 10 g/L, 15 g/L, or 20 g/L sodium chloride. The co-culture system of Dhc and SFB93 was successfully established. With no additional nitrogen source but only nitrogen gas presented, Dhc in the coculture system can continue to perform reductive dechlorination, FL2 reducing TCE to vinyl chloride(VC) and producing ethene, BAV1 can reduce cis-DCE to non-toxic ethene completely. Thus, the coculture system can solve the dilemma of the reduction of reductive dechlorination activity caused by the lack of bioavailable nitrogen sources in the field remediation through the interaction between microorganisms and we can develop a potential TCE biological remediation technology in the future. |
