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Algal Biorefineries pp 187–212Cite as

Tubular Photobioreactors

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Abstract

Considerable progress has been made in the past decade in developing the appropriate biotechnology for microalgal mass cultivation aimed at establishing a new agro-industry. However, until today economic constraints currently limit the industrial exploitation of microalgae for feed, food and biofuel production. Large-scale tubular reactors are being operated in Germany and Israel for the production of Chlorella and Haematococcus respectively. However, because of their high investment costs and energy requirement (particularly for mixing and cooling) their use is limited to the production of high-value products for human nutrition, cosmetics and pharmaceutical applications, and for the preparation of inocula for industrial production of low value commodities (biofuels). Tubular reactors are mandatory for the cultivation of strains that require a strict control of temperature and for the production of biohydrogen and in general volatile compounds. In this chapter, rather than extensively examining the plethora of photobioreactor designs available in the literature, we focus the attention on the main biological and technological constraints affecting their performance, and in the second part of this chapter we briefly describe the tubular reactors that are currently operated at a market size. Finally, principles for guiding optimal photobioreactor design are proposed.

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References

  • Acién Fernández FG, García Camacho F, Sánchez Pérez JA, Fernández Sevilla JM, Molina Grima E (1997) A model for light distribution and average solar irradiance inside outdoor tubular photobioreactors for the microalgal mass culture. Biotechnol Bioeng 55:701–714

    Article  Google Scholar 

  • Acién Fernández FG, García Camacho F, Sánchez Pérez JA, Fernández Sevilla JM, Molina Grima E (1998) Modelling of biomass productivity in tubular photobioreactors for microalgal cultures. Effects of dilution rate, tube diameter and solar irradiance. Biotechnol Bioeng 58:605–611

    Article  Google Scholar 

  • Acién Fernández FG, Fernández Sevilla JM, Molina Grima E (2013) Photobioreactors for the production of microalgae. Rev Environ Sci Biotechnol 12:131–151

    Article  Google Scholar 

  • Amanullah A, Buckland BC, Nienow AW (2004) Mixing in the fermentation and cell culture industries. In: Paul EL, Atiemo-Obeng VA, Kresta SM (eds) Handbook of industrial mixing. Wiley-Interscience, New York, pp 345–390

    Google Scholar 

  • Babcock RW, Malda J, Radway JC (2002) Hydrodynamics and mass transfer in a tubular airlift photobioreactor. J Appl Phycol 14:169–184

    Article  CAS  Google Scholar 

  • Borowitzka MA (1999) Commercial production of microalgae: ponds, tanks, tubes and fermenters. J Biotechnol 70:313–321

    Article  CAS  Google Scholar 

  • Borowitzka MA, Moheimani NR (2013) Algae for biofuels and energy. Developments in applied phycology 5, Springer+Business Media Dordrecht, Dordrecht, p 285

    Google Scholar 

  • Briassoulis D, Panagakis P, Chionidis M, Tzenos M, Lalos D, Tsinos A, Berberidis K, Jacobsen A (2010) An experimental helical–tubular photobioreactor for continuous production of Nannochloropsis sp. Bioresour Technol 101:6768–6777

    Article  CAS  PubMed  Google Scholar 

  • Brindley C, Garcia-Malea MC, Aciér-Fernández FG, Fernández Sevilla JM, García Sánchez JL, Molina Grima E (2004) Influence of power supply in the feasibility of Phaeodactlylum tricornutum cultures. Biotechnol Bioeng 87:723–733

    Article  Google Scholar 

  • Burlew JS (1953) Algal culture from laboratory to pilot plant. Carnegie Institution of Washington Publication N. 600, Carnegie Institution, Washington, DC, pp 235–281

    Google Scholar 

  • Camacho Rubio F, Acién Fernández FG, Sánchez Pérez JA, Garcia Camacho F, Molina Grima E (1999) Prediction of dissolved oxygen and carbon dioxide concentration profiles in tubular photobioreactors for microalgal culture. Biotechnol Bioeng 62:71–86

    Article  Google Scholar 

  • Carney LT, Lane TW (2014) Parasites in algal mass culture. Front Microbiol 5(278):1–8

    Google Scholar 

  • Chini Zittelli G, Biondi N, Rodolfi L, Tredici MR (2013) Photobioreactors for mass production of microalgae. In: Richmond A, Hu Q (eds) Handbook of microalgal culture: applied phycology and biotechnology, 2nd edn. Wiley, Oxford, pp 225–266

    Chapter  Google Scholar 

  • Clarens AF, Resurreccion EP, White MA, Colosi LM (2010) Environmental life cycle comparison of algae to other bioenergy feedstocks. Environ Sci Technol 44:1813–1819

    Article  CAS  PubMed  Google Scholar 

  • Cornet J, Dussap C, Duberteret G (1992) A structural model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: I. Coupling between light transfer and growth kinetics. Biotechnol Bioeng 40:817–825

    Article  CAS  PubMed  Google Scholar 

  • Cuaresma M, Janssen M, Vílchez C, Wijffels RH (2011) Horizontal or vertical photobioreactors? How to improve microalgae photosynthetic efficiency. Biores Technol 102:5129–5137

    Article  CAS  Google Scholar 

  • Day JG, Thomas NJ, Achilles-Day UEM, Leakey RJG (2012) Early detection of protozoan grazers in algal biofuel cultures. Biores Technol 114:715–719

    Article  CAS  Google Scholar 

  • Dillschneider R, Posten C (2013) Closed bioreactors as tools for microalgae production. In: Lee JW (ed) Advanced biofuels and bioproducts. Springer Science + Business Media, New York, pp 629–649

    Chapter  Google Scholar 

  • Fernández Sevilla JM, Acién Fernández FG, Molina Grima E (2010) Biotechnological production of lutein and its applications. Appl Microbiol Biotechnol 86:27–40

    Article  PubMed  Google Scholar 

  • Fernández I, Acién Fernández FG, Berenguel M, Guzmán JL (2014) First principles model of a tubular photobioreactor for microalgal production. Ind Eng Chem Res 53:11121–11136

    Article  Google Scholar 

  • Forehead H, O’Kelly C (2013) Small doses, big troubles: modelling growth dynamics of organisms affecting microalgal production cultures in closed photobioreactors. Biores Technol 129:329–334

    Article  CAS  Google Scholar 

  • Gang Y, Li Y, Shen G, Wang W, Lin C, Wu H, Chen Z (2009) A novel method using CFD to optimize the inner structure parameters of flat photobioreactors. J Appl Phycol 21:719–727

    Article  Google Scholar 

  • Giannelli L, Torzillo G (2012) Hydrogen production with the microalga Chlamydomonas reinhardtii grown in a compact tubular photobioreactor immersed in a scattering nanoparticle suspension. Int J Hyd Energy 37:16951–16961

    Article  CAS  Google Scholar 

  • Grobbelaar JU (1991) The influence of light/dark cycle in mixed algal cultures on their productivity. Bioresour Technol 38:189–194

    Article  Google Scholar 

  • Gudin C, Chaumont D (1983) Solar biotechnology study and development of tubular solar receptors for controlled production of photosynthetic cellular biomass for methane production and specific exocellular biomass. In: Palz W, Pirrwitz D (eds) Energy from biomass. D. Reidel, Dordrecht, pp 184–193

    Google Scholar 

  • Harris L, Tozzi S, Wiley P, Young C, Richardson Tra-My J, Clark K, Trent JD (2013) Potential impact of biofouling on the photobioreactors of the Offshore Membrane Enclosures for Growing Algae (OMEGA) system. Bioresour Technol 144:420–428

    Article  CAS  PubMed  Google Scholar 

  • Hoffman Y, Aflalo C, Zarka A, Gutman J, James T, Boussiba S (2008) Isolation and characterization of a novel chytrid species (phylum Blastocladiomycota), parasitic on the green alga Haematococcus. Mycol Res 112:70–81

    Article  CAS  PubMed  Google Scholar 

  • Hu Q, Guterman H, Richmond A (1996) A flat inclined modular photobioreactor for outdoor mass cultivation of photoautotrophs. Biotechnol Bioeng 51:51–60

    Article  CAS  PubMed  Google Scholar 

  • Huntley ME, Redalje DG (2007) CO2 mitigation and renewable oil from photosynthetic microbes: a new appraisal. Mitig Adapt Strat Glob Chang 12:73–608

    Article  Google Scholar 

  • Jüttner F (1982) Mass cultivation of microalgae and photosynthetic bacteria under sterile conditions. Proc Biochem 7:2–7

    Google Scholar 

  • Kobayashi K, Fujita K (1997) Tube diameter on tubular photobioreactor for microalgal culture and its biomass. J Chem Eng Japan 30:339–341

    Article  CAS  Google Scholar 

  • Kok B (1953) Experiments on photosynthesis by Chlorella in flashing light. In: Burlew JS (ed) Algal culture from laboratory to pilot plant. Carnegie Institution of Washington Publication N. 600, Carnegie Institution, Washington, DC, pp 63–75

    Google Scholar 

  • Kresta SM, Brodkey RS (2004) Turbulence in mixing applications. In: Paul EL, Atiemo-Obeng VA, Kresta SM (eds) Handbook of industrial mixing. Wiley-Interscience, New York, pp 345–390

    Google Scholar 

  • Lardon L, Hélias A, Sialve B, Steyer JP, Bernard O (2009) Lyfe-cycle assessment of biodiesel production from microalgae. Environ Sci Technol 43:6475–6481

    Article  CAS  PubMed  Google Scholar 

  • Laws EA, Terry KL, Wickman J, Chalup MS (1983) A simple algal production system designed to utilize the flashing light effect. Biotechnol Bioeng 25:2319–2335

    Article  CAS  PubMed  Google Scholar 

  • Leupold M, Hindersin S, Gust G, Kerner M, Hanelt D (2013) Influence of mixing and shear stress on Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii. J Appl Phycol 2:485–495

    Article  Google Scholar 

  • Masojídek J, Papáček S, Sergejevová M, Jirka V, Červený C, Kunc J, Korečko J, Verbovikova O, Kopecký J, Štys D, Torzillo G (2003) A closed solar photobioreactor for cultivation of microalgae under supra-high irradiance: basic design and performance. J Appl Phycol 15:239–248

    Article  Google Scholar 

  • Masojídek J, Sergejevová M, Rottnerová K, Jirka V, Korečko J, Kopecký J, Zaťková I, Torzillo G, Štys D (2009) A two-stage solar photobioreactor for cultivation of microalgae based on solar concentrators. J Appl Phycol 21:55–63

    Article  Google Scholar 

  • Molina Grima E, Acién Fernández FG, Camacho G, Chisti Y (1999) Photobioreactors: light regime, mass transfer, and scale-up. J Biotechnol 70:231–247

    Article  CAS  Google Scholar 

  • Molina Grima E, Acién Fernández FG, Camacho G, Camacho Rubio F, Chisti Y (2000) Scale-up of tubular photobioreactors. J Appl Phycol 12:355–368

    Article  Google Scholar 

  • Molina Grima E, Acién Fernández FG, Medina AR (2013) Downstream processing of cell mass and products. In: Richmond A, Hu Q (eds) Handbook of microalgal culture: applied phycology and biotechnology, 2nd edn. Wiley, Oxford, pp 267–309

    Chapter  Google Scholar 

  • Morita M, Watanabe Y, Saiki H (2000) Investigation of photobioreactor design for enhancing the photosynthetic productivity of microalgae. Biotechnol Bioeng 69:63–668

    Google Scholar 

  • Muller-Feuga A, Lemar M, Vermel E, Pradelles R, Rimbaud L, Valiorgue P (2012) Appraisal of a horizontal two-phase flow photobioreactor for continuous production of delicate microalgae species. J Appl Phycol 24:349–355

    Article  CAS  Google Scholar 

  • Nedbal L, Tichý V, Xiong VF, Grobbelaar JU (1986) Microscopic green algae and cyanobacteria in high-frequency intermittent light. J Appl Phycol 8:325–333

    Article  Google Scholar 

  • Norsker NH, Barbosa MJ, Vermuë MH, Wijffels RH (2011) Microalgal production-A closer look at the economics. Biotechnol Adv 29:24–27

    Article  CAS  PubMed  Google Scholar 

  • Olaizola M (2003) Commercial development of microalgal biotechnology: from the test tube to marketplace. Biomol Eng 20:459–466

    Article  CAS  PubMed  Google Scholar 

  • Oncel S, Sabankay M (2012) Microalgal biohydrogen production considering light energy and mixing time as the two key features for scale-up. Bioresour Technol 121:228–234

    Article  CAS  PubMed  Google Scholar 

  • Perner-Nochta I, Posten C (2007) Simulations of light intensity variation in photobioreactors. J Biotechnol 131:276–285

    Article  CAS  PubMed  Google Scholar 

  • Pirt SJ, Kee YK, Walach MR, Pirt MW, Balyuzi HHM, Bazin ML (1983) A tubular bioreactor for photosynthetic production of biomass from carbon dioxide: design and performance. J Chem Tech Biotechnol 33B:35–58

    CAS  Google Scholar 

  • Posten C (2009) Design principles of photo-bioreactors for cultivation of microalgae. Eng Life Sci 3:165–177

    Article  Google Scholar 

  • Pruvost J, Pottier L, Legrand J (2006) Numerical investigation of hydrodynamic and mixing conditions in a torus photobioreactor. Chem Eng Sci 61:4476–4489

    Article  CAS  Google Scholar 

  • Pulz O, Broneske J, Waldeck P (2013) IGV GmbH experience report, industrial production of microalgae under controlled conditions: innovative prospects. In: Richmond A, Hu Q (eds) Handbook of microalgal culture: applied phycology and biotechnology, 2nd edn. Wiley, Oxford, pp 445–460

    Chapter  Google Scholar 

  • Raes EJ, Isdepsky A, Muylaert K, Borowitzka MA, Moheimani NR (2014) Comparison of growth of Tetraselmis in a tubular photobioreactor (Biocoil) and a raceway pond. Appl Phycol 26:247–255

    Article  CAS  Google Scholar 

  • Rego A, Redondo LM, Geraldes V, Costa L, Navalho J, Pereira MT (2015) Control of predators in industrial scale microalgae cultures with pulsed electric fields. Bioelectrochemistry 103:60–64

    Article  CAS  PubMed  Google Scholar 

  • Richmond A (2013) Biological principles of mass cultivation of phototrophic microalgae. In: Richmond A, Hu Q (eds) Handbook of microalgal culture, applied phycology and biotechnology. Wiley & Sons, Ltd. Published 2013 by Blackwell Publishing Ltd., Oxford, UK, pp 171–204

    Google Scholar 

  • Richmond A, Hu Q (2013) Handbook of microalgal culture applied phycology and biotechnology, 2nd edn. Wiley Blackwell, Chichester, p 705

    Book  Google Scholar 

  • Richmond A, Boussiba S, Vonshak V, Kopel R (1993) A new tubular reactor for mass production of microalgae outdoors. J Appl Phycol 5:327–332

    Article  Google Scholar 

  • Robinson LF, Morrison AW (1987) Improvements relating to biomass production. EU Patent 0239272 A2

    Google Scholar 

  • Sánchez Mirón A, Contreras Gómez A, García Camacho F, Molina Grima E, Chisti Y (1999) Comparative evaluation of compact photobioreactors for large-scale monoculture of microalgae. J Biotechnol 70:249–270

    Article  Google Scholar 

  • Scarsella M, Torzillo G, Cicci A, Belotti G, De Filippis P, Bravi M (2012) Mechanical stress tolerance of two microalgae. Proc Biochem 47:1603–1611

    Article  CAS  Google Scholar 

  • Scoma A, Giannelli L, Faraloni C, Torzillo G (2012) Outdoor H2 production in a 50-L tubular photobioreactor by means of a sulfur-deprived culture of the microalga Chlamydomonas reinhardtii. J Biotechnol 157:620–627

    Google Scholar 

  • Šetlík I, Komárek J, Prokeš B (1967) Short account of the activities from 1960 to 1965. In: Nečas J, Lhotský O (eds) Annual report of the laboratory of experimental algology and department of applied algology for the year 1966. Knihtisk, Prague, pp 5–36

    Google Scholar 

  • Terry KL (1986) Photosynthesis in modulated light: quantitative dependence of photosynthetic enhancement on flashing rate. Biotechnol Bioeng 28:988–995

    Article  CAS  PubMed  Google Scholar 

  • Torzillo G (1980) Two years of mass culture of Spirulina maxima in tubular system (in Italian). In: Materassi R (ed) Proceedings of conference “Perspectives of mass cultivation of Spirulina in Italy”. Florence, Accademia dei Georgofili, 20–21 November 1980

    Google Scholar 

  • Torzillo G (1997) Tubular reactors. In: Vonshak A (ed) Spirulina platensis (Arthrospira), physiology, cell biology and biotechnology. Taylor & Francis, London, pp 101–115

    Google Scholar 

  • Torzillo G, Pushparaj B, Bocci F, Balloni W, Materassi R, Florenzano G (1986) Production of Spirulina biomass in closed photobioreactors. Biomass 11:61–74

    Article  Google Scholar 

  • Torzillo G, Bocci F, Pushparaj B, Materassi R (1987) Studies on the production of Spirulina biomass through outdoor culture in tubular photobioreactors. In: Grasso G, Delmon B, Molle JF, Zibetta H (eds) Biomass for energy and industry. Proceedings of the international conference on biomass for energy and industry, Orléans, France, 11–15 May 1987. Elsevier, London/New York, pp 608–614

    Google Scholar 

  • Torzillo G, Carlozzi P, Pushparaj B, Montaini E, Materassi R (1993) A two-plane tubular photobioreactor for outdoor culture of Spirulina. Biotechnol Bioeng 42:891–898

    Article  CAS  PubMed  Google Scholar 

  • Torzillo G, Bernardini P, Masojidek J (1998) On-line monitoring of chlorophyll fluorescence to assess the extent of photoinhibition induced by high oxygen concentration and low temperature and its effect on the productivity of outdoor cultures of Spirulina platensis (cyanobacteria). J Phycol 34:504–510

    Article  CAS  Google Scholar 

  • Torzillo G, Pushparaj B, Masojídek J, Vonshak A (2003) Biological constraints in algal biotechnology. Biotechnol Bioprocess Eng 8:338–348

    Article  CAS  Google Scholar 

  • Torzillo G, Scoma A, Faraloni C, Giannelli L (2014) Advances in the biotechnology of hydrogen production with the microalga Chlamydomonas reinhardtii. Crit Rev Biotechnol. doi:10.3109/07388551.2014.900734

  • Travieso L, Hall DO, Rao KK, Benitez F, Sanchez E, Borja R (2001) A helical tubular photobioreactor producing Spirulina in a semicontinuous mode. Int Biodeter Biodegr 47:151–155

    Article  CAS  Google Scholar 

  • Tredici MR (2004) Mass production of microalgae: photobioreactors. In: Richmond A (ed) Handbook of microalgal cultures, biotechnology and applied phycology. Blackwell Science, Oxford, pp 178–214

    Google Scholar 

  • Tredici MR, Chini Zittelli G (1998) Efficiency of sunlight utilization: tubular versus flat photobioreactors. Biotechnol Bioeng 57:187–197

    Article  CAS  PubMed  Google Scholar 

  • Tredici MR, Chini Zittelli G, Rodolfi L (2010) Photobioreactors. In: Flickinger MC, Anderson S (eds) Encyclopedia of industrial biotechnology: bioprocess, bioseparation, and cell technology, vol 6. Wiley, Hoboken, pp 3821–3838

    Google Scholar 

  • Tredici M, Bassi N, Prussi M, Biondi N, Rodolfi L, Chini Zittelli G, Sampietro G (2015) Energy balance of algae biomass production in a 1-ha “Green Wall Panel” plant: how to produce algae biomass in a closed reactor achieving a high Net Energy Ratio. Appl Energy. http://dx.doi.org/10.1016/J.apenergy.2015.01.086

  • Trent J, Wiley P, Tozzi S, NcKuin B, Reinsch S (2012) The future of biofuels: is it in the bag? Biofuels 3:521–524

    Article  CAS  Google Scholar 

  • Ugwu CU, Aoyagi H, Uchiyama H (2008) Photobioreactors for mass cultivation of algae. Biores Technol 99:4021–4028

    Article  CAS  Google Scholar 

  • Verdelho Vieira V (2012) (Emerging) Industrial production of Nannochloropsis microalgae biomass around the world. http://www.acpnonfood.com/WS8.2-20130429-(Vitor%20Verdelho).pdf. Accessed 12 Mar 2015

  • Vonshak A, Torzillo G, Masojidek J, Boussiba S (2001) Sub-optimal temperature induces photoinhibition in dense outdoor cultures of the alga Monodus subterraneus (Eustigmatophyta). Plant Cell Environ 24:113–118

    Article  Google Scholar 

  • Waldeck P (2012) Closed photobioreactor designs: from lab to industrial scale production of microalgal biomass. Oral presentation at ABO Algae Biomass Summit, Denver, USA, 24–27 September

    Google Scholar 

  • Wang H, Zhang W, Chen L, Wang J, Liu T (2013) The contamination and control of biological pollutants in mass cultivation of microalgae. Biores Technol 128:745–750

    Article  CAS  Google Scholar 

  • Wijffels R, Barbosa MJ (2010) An outlook on microalgal biofuels. Science 329:796–799

    Article  CAS  PubMed  Google Scholar 

  • Wiley P, Harris L, Reinsch S, Tozzi S, Embaye T, Clark K, McKuin B, Kolber Z, Adams R, Kagawa H, Richardson TMJ, Malinowski J, Beal C, Claxton MA, Geiger E, Rask J, Campbell JE, Trent JD (2013) Microalgae cultivation using offshore membrane enclosures for growing algae (OMEGA). J Sustain Bioengy Syst 3:18–32

    Article  Google Scholar 

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Acknowledgements

The research leading to these results has received funding from the European Union Seventh Framework Program (FP7/2007-2013) under grand agreement number 308518 (Cyanofactory).

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Authors and Affiliations

  1. CNR-Istituto per lo Studio degli Ecosistemi – sede di Firenze, Via Madonna del Piano, 10, 50019, Sesto Fiorentino, Italy

    Giuseppe Torzillo & Graziella Chini Zittelli

Authors
  1. Giuseppe Torzillo
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  2. Graziella Chini Zittelli
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Correspondence to Giuseppe Torzillo .

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Editors and Affiliations

  1. Department of Chemical and Biological Engineering, Vanderbilt University, Nashville, Tennessee, USA

    Aleš Prokop

  2. Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, Louisiana, USA

    Rakesh K. Bajpai

  3. Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, Louisiana, USA

    Mark E. Zappi

List of Acronyms

List of Acronyms

AR/AG :

ratio between illuminated area and ground area of the reactor

CFD:

computational fluid dynamics

NHTR:

near-horizontal tubular reactor

LLDPE:

low-density polyethylene

OMEGA:

offshore membrane enclosed growing algae

PBR:

photobioreactor

PE:

photosynthetic efficiency

PFD:

photon flux density

PQ:

plastoquinone

S/V:

surface to volume ratio

SOD:

superoxide-dismutase

wwwPBR:

wind, wavy, wiped tubular photobioreactor

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Torzillo, G., Chini Zittelli, G. (2015). Tubular Photobioreactors. In: Prokop, A., Bajpai, R., Zappi, M. (eds) Algal Biorefineries. Springer, Cham. https://doi.org/10.1007/978-3-319-20200-6_5

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