微藻是目前最有潛力的生物燃料料源之一，然而如何從大量水體中採收微藻仍是一個在商業化過程中之的限制。因此，本研究利用三種絮凝法(pH調控法、氯化鋁添加法及氯化鋁結合生物絮凝劑法)進行含油綠藻Chlorella vulgaris ESP-31之收集，並探討不同的起始微藻濃度、微藻含油量、絮凝劑濃度及pH值對微藻回收的影響，且評估測試其放大操作之可行性。
實驗結果顯示，使用pH調控法時，將pH控制在12可得到較好的絮凝效率，且在較高的起始藻體濃度也可達到較佳的絮凝效率。然而，較高的油脂含量卻會降低pH調控法的絮凝效果。另外，使用氯化鋁絮凝藻體時，愈高的藻體濃度需要愈多的絮凝劑，而油脂含量對起始絮凝速率並沒有很大的影響。將氯化鋁結合生物絮凝劑時，其可大幅增加藻體之絮凝速率，卻會降低其最高絮凝效率。
最後，使用大體積進行絮凝反應時，在綜合各種參考要素後發現，pH調控法是較佳的選擇；且使用此法時，其培養基可再回收使用，不僅降低成本又兼具環保意識，是一舉兩得之方法。

Microalga is a highly promising resource for renewable biofuels production. However, commercialization of microalgal biofuels has been restrained by the high cost involved in the harvesting of the microalgal biomass. In this study, three different flocculation methods were investigated for harvesting oil-rich green microalga Chlorella vulgaris ESP-31. Those methods include flocculation by using pH adjustment, AlCl3 addition, and consecutive treatment using AlCl3 and bioflocculant produced by Bacillus subtilis DYU1. Effects of initial microalga concentrations, lipid contents, concentration of coagulants, and pH values on the flocculation efficiency were also examined. Flocculation experiments were conducted using 40 mL, 250 mL, and 1 L culture to evaluate the feasibility of scale up operation of the developed biomass harvesting technology.
Flocculation with 40 mL microalga culture using pH adjustment and AlCl3 addition suggests that flocculation can provide effective recovery of the microalgal biomass. Adjusting pH at 12.0 was optimal for microalga harvesting and a higher initial microalga concentration was favorable in harvesting efficiency. However, increase in lipid content caused negative effect on the flocculation performance while using pH adjustment method.
When AlCl3 addition was applied for biomass harvesting, more AlCl3 was required for a given degree of flocculation when the initial microalga concentration was higher. There was no clear trend between lipid content and flocculation performances in the chemical flocculation operations. Consecutive treatment using AlCl3 and bioflocculant remarkably accelerated flocculation rate. However, addition of bioflocculant led to a decrease in the highest flocculation efficiency when biomass concentration was 0.80 g/L.
When considering all the aspects of microalgal biomass flocculation, pH adjustment method seems to be the most suitable harvesting method to recover Chlorella vulgaris ESP-31 when 1 L microalga culture was applied. Although the harvesting performance was moderate, the cost was the lowest among the three methods. In addition, by using pH adjustment method to harvest microalga, the clarified culture medium can possibly be reused for the next microalga cultivation, thereby possessing a dual benefits of low cost and high environmental compatibility.

Ahmad, A.L., Yasin, N.H.M., Derek, C.J.C. and Lim, J.K. Microalgae as a sustainable energy source for biodiesel production: A review. Renewable and Sustainable Energy Reviews 15 (1), 584-593. 2011
Amin, S. Review on biofuel oil and gas production processes from microalgae. Energy Conversion and Management 50 (7), 1834-1840. 2009
Ayoub, G.M., Lee, S.-I. and Koopman, B. Seawater induced algal flocculation. Water Research 20 (10), 1265-1271. 1986
Brennan, L. and Owende, P. Biofuels from microalgae--A review of technologies for production, processing, and extractions of biofuels and co-products. Renewable and Sustainable Energy Reviews 14 (2), 557-577. 2010
Chen, C.Y., Yeh, K.L., Aisyah, R., Lee, D.J. and Chang, J.S. Cultivation, photobioreactor design and harvesting of microalgae for biodiesel production: a critical review. Bioresource Technology 102 (1), 71-81. 2011
Chisti, Y. Biodiesel from microalgae. Biotechnology Advances 25 (3), 294-306. 2007
Costa, J.A. and de Morais, M.G. The role of biochemical engineering in the production of biofuels from microalgae. Bioresource Technology 102 (1), 2-9. 2011
Demirbas, A. and Fatih Demirbas, M. Importance of algae oil as a source of biodiesel. Energy Conversion and Management 52 (1), 163-170. 2011
Duan, J. and Gregory, J. Coagulation by hydrolysing metal salts. Advances in Colloid and Interface Science 100-102, 475-502. 2003
Duffy, J.E., Canuel, E.A., Adey, W. and Swaddle, J.P. Biofuels: algae. Science 326 (5958), 1345-1346. 2009
Fellows, C.M. and Doherty, W.O.S. Insights into bridging flocculation. Macromolecular Symposia 231, 1-10. 2006
Greenwell, H.C., Laurens, L.M., Shields, R.J., Lovitt, R.W. and Flynn, K.J. Placing microalgae on the biofuels priority list: a review of the technological challenges. J R Soc Interface 7 (46), 703-726. 2010
Greenwell, H.C., Laurens, L.M., Shields, R.J., Lovitt, R.W. and Flynn, K.J. Placing microalgae on the biofuels priority list: a review of the technological challenges. Journal of the Royal Society Interface 7 (46), 703-726. 2010
Gregory, J. and Duan, J.M. Hydrolyzing metal salts as coagulants. Pure and Applied Chemistry 73 (12), 2017-2026. 2001
Harun, R., Singh, M., Forde, G.M. and Danquah, M.K. Bioprocess engineering of microalgae to produce a variety of consumer products. Renewable and Sustainable Energy Reviews 14 (3), 1037-1047. 2010
Henderson, R.K., Parsons, S.A. and Jefferson, B. Successful Removal of Algae through the Control of Zeta Potential. Separation Science and Technology 43 (7), 1653-1666. 2008
Henderson, R.K., Parsons, S.A. and Jefferson, B. Successful Removal of Algae through the Control of Zeta Potential. Separation Science and Technology 43 (7), 1653 - 1666. 2008
Horiuchi, J.-I., Ohba, I., Tada, K., Kobayashi, M., Kanno, T. and Kishimoto, M. Effective cell harvesting of the halotolerant microalga Dunaliella tertiolecta with pH control. Journal of Bioscience and Bioengineering 95 (4), 412-415. 2003
Kim, D.G., La, H.J., Ahn, C.Y., Park, Y.H. and Oh, H.M. Harvest of Scenedesmus sp. with bioflocculant and reuse of culture medium for subsequent high-density cultures. Bioresource Technology 102 (3), 3163-3168. 2010
Koenraad, M., Vandamme, D., Meesschaert, B. and Foubert, I. Flocculation of Microalgae Using Cationic Starch. Phycologia 48 (4), 63-63. 2009
Kumar, A., Ergas, S., Yuan, X., Sahu, A., Zhang, Q., Dewulf, J., Malcata, F.X. and van Langenhove, H. Enhanced CO2 fixation and biofuel production via microalgae: recent developments and future directions. Trends in Biotechnology 28 (7), 371-380. 2010
Lee, Kim, Kwon, Yoon and Oh. Effects of harvesting method and growth stage on the flocculation of the green alga Botryococcus braunii. Letters in Applied Microbiology 27 (1), 14-18. 1998
Lee, A., Lewis, D. and Ashman, P. Microbial flocculation, a potentially low-cost harvesting technique for marine microalgae for the production of biodiesel. Journal of Applied Phycology 21 (5), 559-567. 2009
Li, Y., Horsman, M., Wang, B., Wu, N. and Lan, C. Effects of nitrogen sources on cell growth and lipid accumulation of green alga <i>Neochloris oleoabundans</i>. Applied Microbiology and Biotechnology 81 (4), 629-636. 2008
Mata, T.M., Martins, A.A. and Caetano, N.S. Microalgae for biodiesel production and other applications: A review. Renewable and Sustainable Energy Reviews 14 (1), 217-232. 2010
Merrill, D.T. and Jorden, R.M. Lime-Induced Reactions in Municipal Wastewaters. Journal of the Water Pollution Control Federation 47 (12), 2783-2808. 1975
Molina-Grima, E., Belarbi, E.H., Acien Fernandez, F.G., Robles Medina, A. and Chisti, Y. Recovery of microalgal biomass and metabolites: process options and economics. Biotechnology Advances 20 (7-8), 491-515. 2003
Muñoz, R. and Guieysse, B. Algal-bacterial processes for the treatment of hazardous contaminants: A review. Water Research 40 (15), 2799-2815. 2006
Nurdogan, Y. and Oswald, W.J. Tube settling of high-rate pond algae. Water Science and Technology 33 (7), 229-241. 1996
Oh, H.-M., Lee, S.J., Park, M.-H., Kim, H.-S., Kim, H.-C., Yoon, J.-H., Kwon, G.-S. and Yoon, B.-D. Harvesting of Chlorella vulgaris using a bioflocculant from Paenibacillus sp. AM49. Biotechnology Letters 23 (15), 1229-1234. 2001
Papazi, A., Makridis, P. and Divanach, P. Harvesting Chlorella minutissima using cell coagulants. Journal of Applied Phycology 22 (3), 349-355. 2010
Pienkos, P.T. and Darzins, A. The promise and challenges of microalgal-derived biofuels. Biofuels, Bioproducts and Biorefining 3 (4), 431-440. 2009
Pittman, J.K., Dean, A.P. and Osundeko, O. The potential of sustainable algal biofuel production using wastewater resources. Bioresource Technology 102 (1), 17-25. 2011
Pushparaj, B., Pelosi, E., Torzillo, G. and Materassi, R. Microbial biomass recovery using a synthetic cationic polymer. Bioresource Technology 43 (1), 59-62. 1993
Salehizadeh, H. and Shojaosadati, S.A. Extracellular biopolymeric flocculants. Recent trends and biotechnological importance. Biotechnol Adv 19 (5), 371-385. 2001
Salehizadeh, H. and Shojaosadati, S.A. Extracellular biopolymeric flocculants: Recent trends and biotechnological importance. Biotechnology Advances 19 (5), 371-385. 2001
Salehizadeh, H., Vossoughi, M. and Alemzadeh, I. Some investigations on bioflocculant producing bacteria. Biochemical Engineering Journal 5 (1), 39-44. 2000
Schenk, P., Thomas-Hall, S., Stephens, E., Marx, U., Mussgnug, J., Posten, C., Kruse, O. and Hankamer, B. Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production. Bioenergy Research 1 (1), 20-43. 2008
Semerjian, G. and Cugliandolo, L.F. Cluster expansions in dilute systems: applications to satisfiability problems and spin glasses. Physical Review E: Statistical, Nonlinear, and Soft Matter Physics 64 (3 Pt 2), 36115. 2001
Semerjian, L. and Ayoub, G.M. High-pH-magnesium coagulation-flocculation in wastewater treatment. Advances in Environmental Research 7 (2), 389-403. 2003
Sharma, B.R., Dhuldhoya, N.C. and Merchant, U.C. Flocculants - an ecofriendly approach. Journal of Polymers and the Environment 14 (2), 195-202. 2006
Singh, A., Nigam, P.S. and Murphy, J.D. Mechanism and challenges in commercialisation of algal biofuels. Bioresource Technology 102 (1), 26-34. 2011
Solomon, B.D. Biofuels and sustainability. Annals of the New York Academy of Sciences 1185, 119-134. 2010
Sorokin, C. and Krauss, R.W. The Effects of Light Intensity on the Growth Rates of Green Algae. Plant Physiol. 33 (2), 109-113. 1958
Sukenik, A. and Shelef, G. Algal autoflocculation--verification and proposed mechanism. Biotechnology and Bioengineering 26 (2), 142-147. 1984
Tilton, R.C., Murphy, J. and Dixon, J.K. The flocculation of algae with synthetic polymeric flocculants. Water Research 6 (2), 155-164. 1972
Uduman, N., Qi, Y., Danquah, M.K., Forde, G.M. and Hoadley, A. Dewatering of microalgal cultures: A major bottleneck to algae-based fuels. Journal of Renewable and Sustainable Energy 2 (1), 12701. 2010
Uduman, N., Qi, Y., Danquah, M.K. and Hoadley, A.F.A. Marine microalgae flocculation and focused beam reflectance measurement. Chemical Engineering Journal 162 (3), 935-940. 2010
Vandamme, D., Pontes, S.C.V., Goiris, K., Foubert, I., Pinoy, L.J.J. and Muylaert, K. Evaluation of electro-coagulation–flocculation for harvesting marine and freshwater microalgae. Biotechnology and Bioengineering. 2011
Widjaja, A., Chien, C.-C. and Ju, Y.-H. Study of increasing lipid production from fresh water microalgae Chlorella vulgaris. Journal of the Taiwan Institute of Chemical Engineers 40 (1), 13-20. 2009
Wijffels, R.H. and Barbosa, M.J. An outlook on microalgal biofuels. Science 329 (5993), 796-799. 2010
Wu, J.-Y. and Ye, H.-F. Characterization and flocculating properties of an extracellular biopolymer produced from a Bacillus subtilis DYU1 isolate. Process Biochemistry 42 (7), 1114-1123. 2007
Wu, Z.B., Wu, X.H., Fu, G.P., Cheng, S.P., He, F. and Deng, P. Comparison of algal removal efficiencies in different ecological treatment systems and their combinations. Huan Jing Ke Xue 27 (2), 241-245. 2006
Yahi, H., Elmaleh, S. and Coma, J. ALGAL FLOCCULATION-SEDIMENTATION BY PH INCREASE IN A CONTINUOUS REACTOR. Water Science and Technology 30 (8), 259-267. 1994
Yang, Z.H., Huang, J., Zeng, G.M., Ruan, M., Zhou, C.S., Li, L. and Rong, Z.G. Optimization of flocculation conditions for kaolin suspension using the composite flocculant of MBFGA1 and PAC by response surface methodology. Bioresour Technol 100 (18), 4233-4239. 2009
Yeh, K.L. and Chang, J.S. Nitrogen starvation strategies and photobioreactor design for enhancing lipid content and lipid production of a newly isolated microalga Chlorella vulgaris ESP-31: Implications for biofuels. Biotechnol J. 2011
Yokoi, H., Arima, T., Hirose, J., Hayashi, S. and Takasaki, Y. Flocculation properties of poly([gamma]-glutamic acid) produced by Bacillus subtilis. Journal of Fermentation and Bioengineering 82 (1), 84-87. 1996
Yokoi, H., Natsuda, O., Hirose, J., Hayashi, S. and Takasaki, Y. Characteristics of a biopolymer flocculant produced by Bacillus sp. PY-90. Journal of Fermentation and Bioengineering 79 (4), 378-380. 1995
Zouboulis, A., Traskas, G. and Samaras, P. Comparison of Efficiency between Poly-aluminium Chloride and Aluminium Sulphate Coagulants during Full-scale Experiments in a Drinking Water Treatment Plant. Separation Science and Technology 43 (6), 1507 - 1519. 2008