在工業製程當中化石燃料廣泛地使用，大量二氧化碳排放至大氣中後造成全球暖化問題。因此，減少大氣中溫室氣體的含量成為現今全球永續經營的課題之一。工業所排出的煙道廢氣中含有大量的二氧化碳並伴隨著一氧化碳與氫氣等氣體，這種組成的氣體稱之為合成氣(Syngas)。而合成氣可透過厭氧生物醱酵將之轉換成有機酸或醇類。本研究便是利用Clostridium ljungdahlii可經由Wood-Ljungdahl pathway進行自營代謝之特性，進行固碳產製乙酸試驗。探討此乙酸菌代謝情形以及是否能順利轉換氫氣與二氧化碳為乙酸，並探討厭氧流體化薄膜反應槽(AFMBR)應用在乙酸菌產製乙酸之可行性。
研究中使用比例7:3的氫氣與二氧化碳混合氣體進行試驗。結果顯示，當環境pH偏中性時，有較好的乙酸產量表現，而pH偏酸性時，不利乙酸生成但會提高乙醇在產物中的比例。先以葡萄糖富養後再提供氫氣與二氧化碳作為能源與碳源，並更換新的營養鹽，乙酸菌可順利從異營轉換成自營代謝路徑，並且解決產物抑制問題。另外，使用GAC吸附與包埋固定化方法以提高細胞密度進行合成氣醱酵試驗，其中GAC吸附固定化法能有效提升乙酸產量，最高產量可達1600 mg/L。而AFMBR能有效截留細胞於反應槽中，避免細胞流失問題。另外提高進氣量亦可提升乙酸產量，最高乙酸產率可達55.1 mmole/day。但越高的進氣量並不會得到越高的乙酸產率，高氣體流量反而會導致乙酸生成率下降。

The global warming problem was caused by large amount of carbon dioxide emission from fossil fuels and industrial process since Industrial Resolution. Therefore, the reduction of greenhouse gas in the atmosphere is an important issue nowadays. In industrial exhaust gas, it usually consists of CO, CO2, and H2, known as syngas. Syngas can be metabolized by acetogenic bacteria under anaerobic condition which is capable to convert syngas into organic acids and alcohols through the Wood-Ljungdahl pathway.
Syngas fermentation carried out by Clostridium ljungdahlii was applied to H2/CO2 (7:3) to produce acetate. The results showed that bacteria had the better acetate production under neutral pH condition. And ethanol proportion in final product was higher under acidic environment. Clostridium ljungdahlii could switch from heterotrophic metabolism with glucose to syngas fermentation, and the product inhibition could be solved by changing fresh medium. In addition, immobilized method could increase cell density effectively. Immobilized cells by GAC could increase acetate production which the maximum concentration was 1600 mg/L. Immobilized cells by PVA entrapment could keep microorganisms in the particle in effect. Anaerobic fluidized membrane bioreactor (AFMBR) was efficient equipment for microbial cell retention in syngas fermentation. Gas flow rate would impact the acetate production. Higher gas flow rate could get better acetate production; the highest acetate productivity reached 55.1 mmole/day. However, too high gas flow rate would have bad effect on acetate production to decrease the production.

Abrini, J., Naveau, H., Nyns, E.-J. Clostridium autoethanogenum, sp. nov., an anaerobic bacterium that produces ethanol from carbon monoxide. Archives of Microbiology, 161(4), 345-351. (1994).
Abubackar, H.N., Veiga, M.C., Kennes, C. Biological conversion of carbon monoxide: rich syngas or waste gases to bioethanol. Biofuels, Bioproducts and Biorefining, 5(1), 93-114. (2011).
Abubackar, H.N., Veiga, M.C., Kennes, C. Ethanol and acetic acid production from carbon monoxide in a Clostridium strain in batch and continuous gas-fed bioreactors. International Journal of Environmental Research and Public Health, 12(1), 1029-1043. (2015).
Adams, M. Vinegar. in: Microbiology of fermented foods, Springer, pp. 1-44. (1998).
Agler, M.T., Wrenn, B.A., Zinder, S.H., Angenent, L.T. Waste to bioproduct conversion with undefined mixed cultures: the carboxylate platform. Trends in Biotechnology, 29(2), 70-78. (2011).
Bengelsdorf, F.R., Straub, M., Dürre, P. Bacterial synthesis gas (syngas) fermentation. Environmental Technology, 34(13-14), 1639-1651. (2013).
Bertsch, J., Müller, V. CO metabolism in the acetogen Acetobacterium woodii. Applied and Environmental Microbiology, 81(17), 5949-5956. (2015).
Braun, M., Mayer, F., Gottschalk, G. Clostridium aceticum (Wieringa), a microorganism producing acetic acid from molecular hydrogen and carbon dioxide. Archives of Microbiology, 128(3), 288-293. (1981).
Bredwell, M.D., Srivastava, P., Worden, R.M. Reactor design issues for synthesis‐gas fermentations. Biotechnology Progress, 15(5), 834-844. (1999).
Chang, J.-S., Lee, K.-S., Lin, P.-J. Biohydrogen production with fixed-bed bioreactors. International Journal of Hydrogen Energy, 27(11), 1167-1174. (2002).
Chen, K.-C., Lin, Y.-F. Immobilization of microorganisms with phosphorylated polyvinyl alcohol (PVA) gel. Enzyme and Microbial Technology, 16(1), 79-83. (1994).
Cho, G.H., Choi, C.Y., Choi, Y.D., Han, M.H. Continuous ethanol production by immobilized yeast in a fluidized reactor. Biotechnology Letters, 3(11), 667-671. (1981).
Christodoulou, X., Velasquez-Orta, S.B. Microbial Electrosynthesis and Anaerobic Fermentation: An Economic Evaluation for Acetic Acid Production from CO2 and CO. Environmental Science & Technology, 50(20), 11234-11242. (2016).
Cortés, C.G., Tzimas, E., Peteves, S. Technologies for coal based hydrogen and electricity co-production power plants with CO2 capture. JRC Scientific and Technical Reports, EUR, 23661. (2009).
Cotter, J.L., Chinn, M.S., Grunden, A.M. Influence of process parameters on growth of Clostridium ljungdahlii and Clostridium autoethanogenum on synthesis gas. Enzyme and Microbial Technology, 44(5), 281-288. (2009).
Couto, N., Rouboa, A., Silva, V., Monteiro, E., Bouziane, K. Influence of the biomass gasification processes on the final composition of syngas. Energy Procedia, 36, 596-606. (2013).
Das, A., Ljungdahl, L.G. Composition and primary structure of the F1F0 ATP synthase from the obligately anaerobic bacterium Clostridium thermoaceticum. Journal of Bacteriology, 179(11), 3746-3755. (1997).
Dave, R., Madamwar, D. Entrapment of lipase in polymer of polyvinyl alcohol-boric acid for esterification in organic media. (2006).
Devarapalli, M., Atiyeh, H.K. A review of conversion processes for bioethanol production with a focus on syngas fermentation. Biofuel Research Journal, 2(3), 268-280. (2015).
Eş, I., Vieira, J.D.G., Amaral, A.C. Principles, techniques, and applications of biocatalyst immobilization for industrial application. Applied Microbiology and Biotechnology, 99(5), 2065-2082. (2015).
Gaddy, J.L. Biological production of ethanol from waste gases with Clostridium ljungdahlii, Google Patents. (2000).
Gaddy, J.L., Clausen, E.C. Clostridiumm ljungdahlii, an anaerobic ethanol and acetate producing microorganism, Google Patents. (1992).
Giorno, L., Drioli, E. Biocatalytic membrane reactors: applications and perspectives. Trends in Biotechnology, 18(8), 339-349. (2000).
IEA. Energy Technology Perspectives 2012, (Ed.) OECD/IEA. Paris. (2012).
Jones, J.H. The cativa™ process for the manufacture of acetic acid. Platinum Metals Review, 44(3), 94-105. (2000).
Juntawang, C., Rongsayamanont, C., Khan, E. Fouling characterization in entrapped cells-based-membrane bioreactor treating wastewater. Separation and Purification Technology, 175, 321-329. (2017).
Köpke, M., Held, C., Hujer, S., Liesegang, H., Wiezer, A., Wollherr, A., Ehrenreich, A., Liebl, W., Gottschalk, G., Dürre, P. Clostridium ljungdahlii represents a microbial production platform based on syngas. Proceedings of the National Academy of Sciences, 107(29), 13087-13092. (2010).
Köpke, M., Mihalcea, C., Liew, F., Tizard, J.H., Ali, M.S., Conolly, J.J., Al-Sinawi, B., Simpson, S.D. 2, 3-Butanediol production by acetogenic bacteria, an alternative route to chemical synthesis, using industrial waste gas. Applied and Environmental Microbiology, 77(15), 5467-5475. (2011).
Kantzow, C., Mayer, A., Weuster-Botz, D. Continuous gas fermentation by Acetobacterium woodii in a submerged membrane reactor with full cell retention. Journal of Biotechnology, 212, 11-18. (2015).
Kundiyana, D.K., Wilkins, M.R., Maddipati, P., Huhnke, R.L. Effect of temperature, pH and buffer presence on ethanol production from synthesis gas by “Clostridium ragsdalei”. Bioresource Technology, 102(10), 5794-5799. (2011).
Le Berre, C., Serp, P., Kalck, P., Torrence, G.P. Acetic Acid. in: Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA. (2014).
Lee, P.-H. Syngas fermentation to ethanol using innovative hollow fiber membrane. (2010).
Liew, F., Martin, M.E., Tappel, R.C., Heijstra, B.D., Mihalcea, C., Köpke, M. Gas fermentation—a flexible platform for commercial scale production of low-carbon-fuels and chemicals from waste and renewable feedstocks. Frontiers in Microbiology, 7. (2016).
Lindley, N., Loubière, P., Pacaud, S., Mariotto, C., Goma, G. Novel products of the acidogenic fermentation of methanol during growth of Eubacterium limosum in the presence of high concentrations of organic acids. Microbiology, 133(12), 3557-3563. (1987).
Luo, Z., Zhou, J. Thermal conversion of biomass. in: Handbook of Climate Change Mitigation, Springer, pp. 1001-1042. (2012).
Mohammadi, M., Mohamed, A., Najafpour, G., Younesi, H., Uzir, M. Clostridium ljungdahlii for production of biofuel from synthesis gas. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 38(3), 427-434. (2016).
Mohammadi, M., Najafpour, G.D., Younesi, H., Lahijani, P., Uzir, M.H., Mohamed, A.R. Bioconversion of synthesis gas to second generation biofuels: a review. Renewable and Sustainable Energy Reviews, 15(9), 4255-4273. (2011).
Mohammadi, M., Younesi, H., Najafpour, G., Mohamed, A.R. Sustainable ethanol fermentation from synthesis gas by Clostridium ljungdahlii in a continuous stirred tank bioreactor. Journal of Chemical Technology and Biotechnology, 87(6), 837-843. (2012).
Molitor, B., Richter, H., Martin, M.E., Jensen, R.O., Juminaga, A., Mihalcea, C., Angenent, L.T. Carbon recovery by fermentation of CO-rich off gases–Turning steel mills into biorefineries. Bioresource Technology, 215, 386-396. (2016).
Pierce, E., Xie, G., Barabote, R.D., Saunders, E., Han, C.S., Detter, J.C., Richardson, P., Brettin, T.S., Das, A., Ljungdahl, L.G. The complete genome sequence of Moorella thermoacetica (f. Clostridium thermoaceticum). Environmental Microbiology, 10(10), 2550-2573. (2008).
Ragsdale, S.W., Pierce, E. Acetogenesis and the Wood–Ljungdahl pathway of CO2 fixation. Biochimica et Biophysica Acta (BBA)-Proteins and Proteomics, 1784(12), 1873-1898. (2008).
Richter, H., Martin, M.E., Angenent, L.T. A two-stage continuous fermentation system for conversion of syngas into ethanol. Energies, 6(8), 3987-4000. (2013).
Sano, K.i., Uchida, H., Wakabayashi, S. A new process for acetic acid production by direct oxidation of ethylene. Catalysis Surveys from Asia, 3(1), 55-60. (1999).
Schiel-Bengelsdorf, B., Dürre, P. Pathway engineering and synthetic biology using acetogens. FEBS Letters, 586(15), 2191-2198. (2012).
Shen, Y., Brown, R., Wen, Z. Syngas fermentation of Clostridium carboxidivoran P7 in a hollow fiber membrane biofilm reactor: Evaluating the mass transfer coefficient and ethanol production performance. Biochemical Engineering Journal, 85, 21-29. (2014).
Sim, J.H., Kamaruddin, A.H., Long, W.S., Najafpour, G. Clostridium aceticum—A potential organism in catalyzing carbon monoxide to acetic acid: Application of response surface methodology. Enzyme and Microbial Technology, 40(5), 1234-1243. (2007).
Smith, D.R., Doucette-Stamm, L.A., Deloughery, C., Lee, H., Dubois, J., Aldredge, T., Bashirzadeh, R., Blakely, D., Cook, R., Gilbert, K. Complete genome sequence of Methanobacterium thermoautotrophicum deltaH: functional analysis and comparative genomics. Journal of Bacteriology, 179(22), 7135-7155. (1997).
Solomon, S. Climate change 2007-the physical science basis: Working group I contribution to the fourth assessment report of the IPCC. Cambridge University Press. (2007).
Stocker, T. Climate change 2013: the physical science basis: Working Group I contribution to the Fifth assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press. (2014).
Svetlichny, V., Sokolova, T., Gerhardt, M., Ringpfeil, M., Kostrikina, N., Zavarzin, G. Carboxydothermus hydrogenoformans gen. nov., sp. nov., a CO-utilizing thermophilic anaerobic bacterium from hydrothermal environments of Kunashir Island. Systematic and Applied Microbiology, 14(3), 254-260. (1991).
Tanner, R.S., Miller, L.M., Yang, D. Clostridium ljungdahlii sp. nov., an acetogenic species in clostridial rRNA homology group I. International Journal of Systematic and Evolutionary Microbiology, 43(2), 232-236. (1993).
Tirado-Acevedo, O., Cotter, J., Chinn, M., Grunden, A. Influence of carbon source preadaptation on Clostridium ljungdahlii growth and product formation. J Bioprocess Biotechniq S, 2, 001. (2011).
Uffen, R.L. Metabolism of carbon monoxide by Rhodopseudomonas gelatinosa: cell growth and properties of the oxidation system. Journal of Bacteriology, 155(3), 956-965. (1983).
UN. Framework Convention on Climate Change (COP21). (2015).
Ungerman, A.J., Heindel, T.J. Carbon monoxide mass transfer for syngas fermentation in a stirred tank reactor with dual impeller configurations. Biotechnology Progress, 23(3), 613-620. (2007).
Van der Drift, A., Boerrigter, H. Synthesis gas from biomass for fuels and chemicals. ECN Biomass, Coal and Environmental Research. (2006).
Vandecasteele, J. Experimental and modelling study of pure-culture syngas fermentation for biofuels production. (2016).
Water, G. Process Technologies. Handbook of Industrial Water Treatment. (2009).
Whitham, J.M., Tirado-Acevedo, O., Chinn, M.S., Pawlak, J.J., Grunden, A.M. Metabolic response of Clostridium ljungdahlii to oxygen exposure. Applied and Environmental Microbiology, 81(24), 8379-8391. (2015).
Xu, D. Syngas Impurity Effects on Cell Growth, Enzymatic Activities and Ethanol Production via Fermentation. (2012).
Xu, S., Fu, B., Zhang, L., Liu, H. Bioconversion of H2/CO2 by acetogen enriched cultures for acetate and ethanol production: the impact of pH. World Journal of Microbiology and Biotechnology, 31(6), 941-950. (2015).
Younesi, H., Najafpour, G., Mohamed, A.R. Ethanol and acetate production from synthesis gas via fermentation processes using anaerobic bacterium, Clostridium ljungdahlii. Biochemical Engineering Journal, 27(2), 110-119. (2005).
Zhang, F., Ding, J., Shen, N., Zhang, Y., Ding, Z., Dai, K., Zeng, R.J. In situ hydrogen utilization for high fraction acetate production in mixed culture hollow-fiber membrane biofilm reactor. Applied Microbiology and Biotechnology, 97(23), 10233-10240. (2013).
Zhang, L.-S., Wu, W.-z., Wang, J.-l. Immobilization of activated sludge using improved polyvinyl alcohol (PVA) gel. Journal of Environmental Sciences, 19(11), 1293-1297. (2007a).
Zhang, Z.-P., Tay, J.-H., Show, K.-Y., Yan, R., Liang, D.T., Lee, D.-J., Jiang, W.-J. Biohydrogen production in a granular activated carbon anaerobic fluidized bed reactor. International Journal of Hydrogen Energy, 32(2), 185-191. (2007b).
陳國誠. 生物固定化技術與產業應用. 茂昌圖書有限公司, 台北市. (2000).