Support for this research was provided by USDA National Institute of Food and Agriculture Hatch Project ALA0HIGGINS and the Auburn University Offices of the Provost, the Vice President for Research, and the Samuel Ginn College of Engineering. Support was also provided by NSF grant CBET-1438211.

1. Setup of Bubble Column Photobioreactors
<ol>
	<li>Construct a set of vented lids from the plastic lids that came with the 1 L glass bottles and hybridization tubes (see Figure 1 for schematic and photos). Construct lids for the humidifier, mixing trap, each air lift photobioreactor, and each bottle reactor.
	<ol>
		<li>Drill &#188;&#8221; holes in the lid: 2 holes are needed for bioreactor and humidifier lids; 3 holes are needed for the mixing trap.</li>
		<li>Slip a &#188;&#8221; O-rin...

<ol>
	<li>Prandini, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+nutrient+removal+from+swine+wastewater+digestate+coupled+to+biogas+purification+by+microalgae+Scenedesmus+spp.">Enhancement of nutrient removal from swine wastewater digestate coupled to biogas purification by microalgae Scenedesmus spp.</a> Bioresource Technology. , 67-75 (2016).</li><li>Liu, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phycoremediation+of+dairy+and+winery+wastewater+using+Diplosphaera+sp.+MM1.">Phycoremediation of dairy and winery wastewater using Diplosphaera sp. MM1.</a> Journal of Applied Phycology. 28 (6), 3331-3341 (2016).</li><li>Passero, M., Cragin, B., Coats, E. R., McDonald, A. G., Feris, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dairy+Wastewaters+for+Algae+Cultivation,+Polyhydroxyalkanote+Reactor+Effluent+Versus+Anaerobic+Digester+Effluent.">Dairy Wastewaters for Algae Cultivation, Polyhydroxyalkanote Reactor Effluent Versus Anaerobic Digester Effluent.</a> BioEnergy Research. 8 (4), 1647-1660 (2015).</li><li>Hodgskiss, L. H., Nagy, J., Barnhart, E. P., Cunningham, A. B., Fields, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cultivation+of+a+native+alga+for+biomass+and+biofuel+accumulation+in+coal+bed+methane+production+water.">Cultivation of a native alga for biomass and biofuel accumulation in coal bed methane production water.</a> Algal Research. 19, 63-68 (2016).</li><li>Gao, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oil+accumulation+mechanisms+of+the+oleaginous+microalga+Chlorella+protothecoides+revealed+through+its+genome,+transcriptomes,+and+proteomes.">Oil accumulation mechanisms of the oleaginous microalga Chlorella protothecoides revealed through its genome, transcriptomes, and proteomes.</a> BMC Genomics. 15, (2014).</li><li>Burch, A. R., Franz, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combined+nitrogen+limitation+and+hydrogen+peroxide+treatment+enhances+neutral+lipid+accumulation+in+the+marine+diatom+Phaeodactylum+tricornutum.">Combined nitrogen limitation and hydrogen peroxide treatment enhances neutral lipid accumulation in the marine diatom Phaeodactylum tricornutum.</a> Bioresource Technology. 219, 559-565 (2016).</li><li>Brennan, L., Owende, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofuels+from+microalgae--A+review+of+technologies+for+production,+processing,+and+extractions+of+biofuels+and+co-products.">Biofuels from microalgae--A review of technologies for production, processing, and extractions of biofuels and co-products.</a> Renewable Sustainable Energy Reviews. 14 (2), 557-577 (2009).</li><li>Branyikova, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microalgae+-+Novel+highly+efficient+starch+producers.">Microalgae - Novel highly efficient starch producers.</a> Biotechnology and Bioengineering. 108 (4), 766-776 (2010).</li><li>Chalima, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Utilization+of+Volatile+Fatty+Acids+from+Microalgae+for+the+Production+of+High+Added+Value+Compounds.">Utilization of Volatile Fatty Acids from Microalgae for the Production of High Added Value Compounds.</a> Fermentation. 3 (4), (2017).</li><li>Harun, R., Singh, M., Forde, G. M., Danquah, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioprocess+engineering+of+microalgae+to+produce+a+variety+of+consumer+products.">Bioprocess engineering of microalgae to produce a variety of consumer products.</a> Renewable and Sustainable Energy Reviews. 14 (3), 1037-1047 (2010).</li><li>Liu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+new+method+for+genetic+transformation+of+the+green+alga+Chlorella+ellipsoidea.">Development of a new method for genetic transformation of the green alga Chlorella ellipsoidea.</a> Molecular biotechnology. 54 (2), 211-219 (2013).</li><li>Cheng, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutate+Chlorella+sp.+by+nuclear+irradiation+to+fix+high+concentrations+of+CO2.">Mutate Chlorella sp. by nuclear irradiation to fix high concentrations of CO2.</a> Bioresource Technology. 136, 496-501 (2013).</li><li>Davis, R., Aden, A., Pienkos, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Techno-economic+analysis+of+autotrophic+microalgae+for+fuel+production.">Techno-economic analysis of autotrophic microalgae for fuel production.</a> Applied Energy. 88 (10), 3524-3531 (2011).</li><li>Sales, C. M., Au, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+Scale+in+a+Photosynthetic+Reactor+System+for+Algal+Remediation+of+Wastewater.">Comparison of Scale in a Photosynthetic Reactor System for Algal Remediation of Wastewater.</a> Journal of Visualized Experiments. (121), e55256 (2017).</li><li>Higgins, B. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cofactor+symbiosis+for+enhanced+algal+growth,+biofuel+production,+and+wastewater+treatment.">Cofactor symbiosis for enhanced algal growth, biofuel production, and wastewater treatment.</a> Algal Research. 17, 308-315 (2016).</li><li>Higgins, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Algal-bacterial+synergy+in+treatment+of+winery+wastewater.">Algal-bacterial synergy in treatment of winery wastewater.</a> Nature Clean Water. 1 (6), (2017).</li><li>Higgins, B. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+thiamine+metabolites+and+spent+medium+from+Chlorella+sorokiniana+on+metabolism+in+the+green+algae+Auxenochlorella+prototheciodes.">Impact of thiamine metabolites and spent medium from Chlorella sorokiniana on metabolism in the green algae Auxenochlorella prototheciodes.</a> Algal Research. 33, 197-208 (2018).</li><li>L&#233;pinay, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+insight+on+interactions+between+bacteria+and+the+marine+diatom+Haslea+ostrearia:+Algal+growth+and+metabolomic+fingerprinting.">First insight on interactions between bacteria and the marine diatom Haslea ostrearia: Algal growth and metabolomic fingerprinting.</a> Algal Research. 31, 395-405 (2018).</li><li>Franchino, M., Comino, E., Bona, F., Riggio, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+three+microalgae+strains+and+nutrient+removal+from+an+agro-zootechnical+digestate.">Growth of three microalgae strains and nutrient removal from an agro-zootechnical digestate.</a> Chemosphere. 92 (6), 738-744 (2013).</li><li>Choix, F. J., Lopez-Cisneros, C. G., Mendez-Acosta, H. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Azospirillum+brasilense+Increases+CO2+Fixation+on+Microalgae+Scenedesmus+obliquus,+Chlorella+vulgaris,+and+Chlamydomonas+reinhardtii+Cultured+on+High+CO2+Concentrations.">Azospirillum brasilense Increases CO2 Fixation on Microalgae Scenedesmus obliquus, Chlorella vulgaris, and Chlamydomonas reinhardtii Cultured on High CO2 Concentrations.</a> Microbial Ecology. 76 (2), 430-442 (2018).</li><li>Higgins, B., VanderGheynst, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Escherichia+coli+on+mixotrophic+growth+of+Chlorella+minutissima+and+production+of+biofuel+precursors.">Effects of Escherichia coli on mixotrophic growth of Chlorella minutissima and production of biofuel precursors.</a> PLoS One. 9 (5), e96807 (2014).</li><li>Higgins, B., Thornton-Dunwoody, A., Labavitch, J. M., VanderGheynst, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microplate+assay+for+quantitation+of+neutral+lipids+in+extracts+from+microalgae.">Microplate assay for quantitation of neutral lipids in extracts from microalgae.</a> Analytical Biochemistry. 465, 81-89 (2014).</li><li>Tanadul, O. U., Vandergheynst, J. S., Beckles, D. M., Powell, A. L., Labavitch, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+elevated+CO2+concentration+on+the+quality+of+algal+starch+as+a+potential+biofuel+feedstock.">The impact of elevated CO2 concentration on the quality of algal starch as a potential biofuel feedstock.</a> Biotechnology and Bioengineering. 111 (7), 1323-1331 (2014).</li><li>Folch, J., Lees, M., Sloane Stanley, G. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+method+for+the+isolation+and+purification+of+total+lipides+from+animal+tissues.">A simple method for the isolation and purification of total lipides from animal tissues.</a> Journal of Biological Chemistry. 226 (1), 497-509 (1957).</li><li>Higgins, B. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Informatics+for+improved+algal+taxonomic+classification+and+research:+A+case+study+of+UTEX+2341.">Informatics for improved algal taxonomic classification and research: A case study of UTEX 2341.</a> Algal Research. 12, 545-549 (2015).</li><li>Garrett, R. H., Grisham, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Biochemistry. , 578-730 (2012).</li><li>de-Bashan, L. E., Trejo, A., Huss, V. A. R., Hernandez, J. -. P., Bashan, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chlorella+sorokiniana+UTEX+2805,+a+heat+and+intense,+sunlight-tolerant+microalga+with+potential+for+removing+ammonium+from+wastewater.">Chlorella sorokiniana UTEX 2805, a heat and intense, sunlight-tolerant microalga with potential for removing ammonium from wastewater.</a> Bioresource Technology. 99 (11), 4980-4989 (2008).</li><li>Wang, Q., Higgins, B., Ji, H., Zhao, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Annual International Meeting of the ASABE. , (2018).</li></ol>

The authors have nothing to disclose.

The most important consideration when culturing algae is an understanding of the specific needs of the organism or group of organisms. The algae cultivation system described here can be used to culture a wide range of algae but the specific abiotic factors (temperature, media, pH, light intensity, CO2 level, aeration rate) need to be adjusted to the needs of the organism. Note the parameters described here were used for the cultivation of Chlorella and Auxenochlorella. These organisms are of ...

The application of microalgae in engineering and biotechnology has attracted great interest in recent years. Microalgae are being studied for use in wastewater treatment1,2,3,4, biofuel production5,6,7,8, and the production of nutraceuticals and other high value products9,10. Algae are also being genetically modified at greater rates in an effort to improve their fitness for specific engineering applications11,12. Consequently, there is great interest in experimentation with industrially relevant organisms in controlled settings. The purpose of this method is to communicate an effective approach to culture microalgae in a controlled laboratory environment, and to measure the growth and neutral lipid content of that algae. Improving growth rates and neutral lipid content of microalgae have been identified as two key bottlenecks toward commercialization of algal biofuels13.
A wide range of approaches have been used to culture algae for experimental purposes. In general, these approaches can be divided between large-scale outdoor cultivation and small-scale indoor cultivation. Outdoor cultivation in photobioreactors and open ponds is appropriate for experimentation aimed at scaling up processes that have already been proven at laboratory scale (e.g., to test scale-up of a new high-lipid strain of algae)14. However, indoor small-scale cultivation is appropriate when developing new or improved algae strains or performing experiments aimed at understanding biological mechanisms. In these latter cases, a high-degree of experimental control is required to tease out subtle changes in biological behavior. To that end, axenic cultures are often required in order to minimize the complex biotic factors associated with other organisms (e.g. bacteria, other algae) that inevitably grow in large-scale outdoor systems. Even when studying interactions among algae and other organisms, we have found that use of highly-controlled experimental conditions is helpful when examining molecular exchange among organisms15,16,17.
Within the category of small-scale indoor algae cultivation, a range of approaches have been used. Perhaps the most common approach is to grow algae in Erlenmeyer flasks on a shaker table beneath a light bank18,19. Exchange of oxygen and CO2 takes place by passive diffusion through a foam plug in the top of the flask. Some researchers have improved this set-up through active aeration of the flasks20. Another approach is to cultivate algae in bottles, mixed by stir bar and active aeration. Despite their simplicity, we have found that the use of flasks and bottles often leads to inconsistent results among biological replicates. Presumably this is due to position effects - different positions receive different amounts of light, which also affect internal reactor temperatures. Daily rotation of reactors to new positions can help but does not alleviate the problem because certain stages of algae growth (e.g., early exponential) are more sensitive to positional effects than others (e.g., log phase).
On the opposite side of the spectrum of technological sophistication are fully-controlled commercial photobioreactors. These systems continuously monitor and adjust conditions in the reactor to optimize algae growth. They have programmable lighting, real-time temperature control, and pH control. Unfortunately, they are expensive and typically cost several thousand dollars per reactor. Most scientific and engineering journals require biological replication of results, necessitating the purchase of multiple bioreactors. We present here a bubble column reactor system that bridges the divide between the simple (flask) and sophisticated (fully-controlled bioreactor) approaches for lab-scale algae cultivation. Bubble columns use rising gas bubbles to facilitate gas exchange and mix the reactor. This approach provides some degree of control over the lighting and temperature but does so in a way that is cost-effective. Moreover, we have found this system to yield highly consistent results among biological replicates, reducing the required number of biological replicates needed in order to obtain statistically significant results when compared to the flask or bottle approach. We have also used this system to successfully cultivate mixtures of algae and bacteria21. In addition to algae cultivation, we outline a procedure for measuring the neutral lipid content in the cultured algae. The latter method has been published elsewhere22, but we include the procedure here to provide step-by-step instructions for how to employ it successfully.

<table>
	<tbody>
		<tr>
			<td>Supplies for airlift photobioreactor setup</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>1 L Pyrex bottles</td>
			<td>Corning</td>
			<td>16157-191</td>
			<td>For bottle reactors, humidifiers</td>
		</tr>
		<tr>
			<td>1/2&#34; hose clamp</td>
			<td>Home Depot</td>
			<td>UC953A</td>
			<td>or equivalent</td>
		</tr>
		<tr>
			<td>1/4&#34; female luer to barb</td>
			<td>Nordson biomedical</td>
			<td>Nordson FTLL360-6005</td>
			<td>1/4&#34; ID, PP</td>
		</tr>
		<tr>
			<td>1/4&#34; ID, 3/8&#34; OD autoclaveable PVC tubing</td>
			<td>Thermo-Nalgene</td>
			<td>63013-244</td>
			<td>50&#39;</td>
		</tr>
		<tr>
			<td>1/4&#34; in O-rings</td>
			<td>Grainger</td>
			<td>1REC5</td>
			<td>#010 Medium Hard Silicone O-Ring, 0.239&#34; I.D., 0.379&#34;O.D.</td>
		</tr>
		<tr>
			<td>1/8&#34; Female luer to barb</td>
			<td>Nordson biomedical</td>
			<td>FTLL230-6005</td>
			<td></td>
		</tr>
		<tr>
			<td>1/8&#34; ID, 1/4&#34; OD autoclaveable PVC tubing</td>
			<td>Thermo-Nalgene</td>
			<td>63013-608</td>
			<td>250&#39;</td>
		</tr>
		<tr>
			<td>1/8&#34; male spinning luer to barb</td>
			<td>Nordson biomedical</td>
			<td>MLRL013-6005</td>
			<td></td>
		</tr>
		<tr>
			<td>1/8&#34; multiport barb</td>
			<td>Nordson biomedical</td>
			<td>4PLL230-6005</td>
			<td>1/8&#34; multiport barb</td>
		</tr>
		<tr>
			<td>1/8&#34; NPT to barb</td>
			<td>Nordson biomedical</td>
			<td>18230-6005</td>
			<td>1/8&#34; 200 series barb</td>
		</tr>
		<tr>
			<td>1/8&#34; panel mount luer</td>
			<td>Nordson biomedical</td>
			<td>Nordson MLRLB230-6005</td>
			<td>1/8&#34;, PP</td>
		</tr>
		<tr>
			<td>10 gallon fish tank</td>
			<td>Walmart</td>
			<td>802262</td>
			<td>Can hold up to 8 bioreactors depending on layout</td>
		</tr>
		<tr>
			<td>100-1000 ccm flow meter</td>
			<td>Dwyer</td>
			<td>RMA-13-SSV</td>
			<td>For bottle reactors</td>
		</tr>
		<tr>
			<td>2 ft fluorescent light bank</td>
			<td>Agrobrite</td>
			<td>FLT24 T5</td>
			<td></td>
		</tr>
		<tr>
			<td>200-2500 ccm flow meter</td>
			<td>Dwyer</td>
			<td>RMA-14-SSV</td>
			<td>For air regulation upstream of humidifier</td>
		</tr>
		<tr>
			<td>250 mL Pyrex bottles</td>
			<td>Corning</td>
			<td>16157-136</td>
			<td>For gas mixing after humidifier</td>
		</tr>
		<tr>
			<td>50-500 ccm flow meter</td>
			<td>Dwyer</td>
			<td>RMA-12-SSV</td>
			<td>For hybridization tube reactors</td>
		</tr>
		<tr>
			<td>5-50 ccm flow meter</td>
			<td>Dwyer</td>
			<td>RMA-151-SSV</td>
			<td>For CO2 flow rate control</td>
		</tr>
		<tr>
			<td>Air filters 0.2 &#181;m</td>
			<td>Whatman/ Fisher</td>
			<td>09-745-1A</td>
			<td>Polyvent, 28 mm, 0.2 &#181;m, PTFE, 50 pack</td>
		</tr>
		<tr>
			<td>Check valves</td>
			<td>VWR</td>
			<td>89094-714</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning lids for pyrex bottles</td>
			<td>VWR</td>
			<td>89000-233</td>
			<td>10 GL45 lids</td>
		</tr>
		<tr>
			<td>Female luer endcap</td>
			<td>Nordson biomedical</td>
			<td>Nordson FTLLP-6005</td>
			<td>Female stable PP</td>
		</tr>
		<tr>
			<td>Hybridization tubes</td>
			<td>Corning</td>
			<td>32645-030</td>
			<td>35x300 mm, pack of 2</td>
		</tr>
		<tr>
			<td>Light timer</td>
			<td>Walmart</td>
			<td>556393626</td>
			<td></td>
		</tr>
		<tr>
			<td>Locknuts</td>
			<td>Nordson biomedical</td>
			<td>Nordson LNS-3</td>
			<td>1/4&#34;, red nylon</td>
		</tr>
		<tr>
			<td>Low profile magnetic stirrer</td>
			<td>VWR</td>
			<td>10153-690</td>
			<td>Low profile magnetic stirrer</td>
		</tr>
		<tr>
			<td>Male luer endcap</td>
			<td>Nordson biomedical</td>
			<td>Nordson LP4-6005</td>
			<td>Male plug PP</td>
		</tr>
		<tr>
			<td>Spinning luer lock ring</td>
			<td>Nordson biomedical</td>
			<td>Nordson FSLLR-6005</td>
			<td></td>
		</tr>
		<tr>
			<td>Stir bars - long</td>
			<td>VWR</td>
			<td>58949-040</td>
			<td>38.1 mm, for bottle reactors</td>
		</tr>
		<tr>
			<td>Stir bars - medium</td>
			<td>VWR</td>
			<td>58949-034</td>
			<td>25 mm, for hyridization tubes</td>
		</tr>
		<tr>
			<td>Supplies and reagents for culturing algae</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>0.2 &#181;m filters</td>
			<td>VWR</td>
			<td>28145-491</td>
			<td>13 mm, PTFE, for filtering spent media from daily culture sampling</td>
		</tr>
		<tr>
			<td>1 mL syringes</td>
			<td>Air-tite</td>
			<td>89215-216</td>
			<td>For filtering spent media from daily culture sampling</td>
		</tr>
		<tr>
			<td>1.5 mL tubes</td>
			<td>VWR</td>
			<td>87003-294</td>
			<td>Sterile (or equivalent)</td>
		</tr>
		<tr>
			<td>10 mL Serological pipettes</td>
			<td>Greiner Bio-One</td>
			<td>82050-482</td>
			<td>Sterile (or equivalent)</td>
		</tr>
		<tr>
			<td>100 mm plates</td>
			<td>VWR</td>
			<td>25384-342</td>
			<td>100x15 mm stackable petri dishes, sterile</td>
		</tr>
		<tr>
			<td>15 mL tubes</td>
			<td>Greiner Bio-One</td>
			<td>82050-276</td>
			<td>Sterile (or equivalent), polypropylene</td>
		</tr>
		<tr>
			<td>2 mL Serological pipette tips</td>
			<td>Greiner Bio-One</td>
			<td>82051-584</td>
			<td>Sterile (or equivalent)</td>
		</tr>
		<tr>
			<td>2 mL tubes</td>
			<td>VWR</td>
			<td>87003-298</td>
			<td>Sterile (or equivalent)</td>
		</tr>
		<tr>
			<td>50 mL tubes</td>
			<td>Greiner Bio-One</td>
			<td>82050-348</td>
			<td>Sterile (or equivalent), polypropylene</td>
		</tr>
		<tr>
			<td>96 well microplate</td>
			<td>Greiner Bio-One</td>
			<td>89089-578</td>
			<td>Polystyrene with lid, flat bottom</td>
		</tr>
		<tr>
			<td>Inocculating loops</td>
			<td>VWR</td>
			<td>80094-478</td>
			<td>Sterile (or equivalent)</td>
		</tr>
		<tr>
			<td>Liquid carbon dioxide tank and regulator</td>
			<td>Airgas</td>
			<td>CD-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Supplies and reagents for lipid extraction and neutral lipid assay</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2 mL bead tubes</td>
			<td>VWR</td>
			<td>10158-556</td>
			<td>Polypropylene tube w/ lid</td>
		</tr>
		<tr>
			<td>96 well microplates</td>
			<td>Greiner Bio-One</td>
			<td>82050-774</td>
			<td>Polypropylene, flat bottom</td>
		</tr>
		<tr>
			<td>Bleach</td>
			<td>Walmart</td>
			<td>550646751</td>
			<td>Only use regular bleach, not cleaning bleach</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>BDH</td>
			<td>BDH1109-4LG</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide</td>
			<td>BDH</td>
			<td>BDH1115-1LP</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>BDH</td>
			<td>BDH1133-1LP</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>BDH</td>
			<td>BDH20864.400</td>
			<td></td>
		</tr>
		<tr>
			<td>Nile red</td>
			<td>VWR</td>
			<td>TCN0659-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur pipette tips</td>
			<td>VWR</td>
			<td>14673-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>BDH</td>
			<td>BDH9286-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Vegetable oil</td>
			<td>Walmart</td>
			<td>9276383</td>
			<td>Any vegetable oil should work as long as it is fresh</td>
		</tr>
		<tr>
			<td>Zirconia/ silica beads (0.5 mm diameter)</td>
			<td>Biospec products</td>
			<td>11079105z</td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Mettler-Toledo</td>
			<td>XS205DU</td>
			<td>Capable of at least 4 decimal accuracy</td>
		</tr>
		<tr>
			<td>Bead homogenizer</td>
			<td>Omni</td>
			<td>19-040E</td>
			<td></td>
		</tr>
		<tr>
			<td>Benchtop micro centrifuge</td>
			<td>Thermo</td>
			<td>Heraeus Fresco 21 with 24x2</td>
			<td>Including rotor capable of handling 1.5 and 2 mL tubes</td>
		</tr>
		<tr>
			<td>Dry block heater</td>
			<td>VWR</td>
			<td>75838-282</td>
			<td>Including dry block for a microplate</td>
		</tr>
		<tr>
			<td>Freeze dryer</td>
			<td>Labconco</td>
			<td>7670520</td>
			<td>2.5L freeze drying system</td>
		</tr>
		<tr>
			<td>Large benchtop centrifuge</td>
			<td>Thermo</td>
			<td>Heraeus Megafuge 16R Tissue</td>
			<td>Including rotors capable of handling 400 mL bottles, 50 mL tubes, and 15 mL tubes</td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>Molecular Devices</td>
			<td>SpectraMax M2</td>
			<td>Capable of reading absorbance and fluorescence</td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>VWR</td>
			<td>10153-838</td>
			<td></td>
		</tr>
	</tbody>
</table>

cultivation of green microalgae in bubble column photobioreactors and an assay for neutral lipids

There is significant interest in the study of microalgae for engineering applications such as the production of biofuels, high value products, and for the treatment of wastes. As most new research efforts begin at laboratory scale, there is a need for cost-effective methods for culturing microalgae in a reproducible manner. Here, we communicate an effective approach to culture microalgae in laboratory-scale photobioreactors, and to measure the growth and neutral lipid content of that algae. Instructions are also included on how to set up the photobioreactor system. Although the example organisms are species of Chlorella and Auxenochlorella, this system can be adapted to cultivate a wide range of microalgae, including co-cultures of algae with non-algae species. Stock cultures are first grown in bottles to produce inoculum for the photobioreactor system. Algae inoculum is concentrated and transferred to photobioreactors for cultivation in batch mode. Samples are collected daily for the optical density readings. At the end of the batch culture, cells are harvested by centrifuge, washed, and freeze dried to obtain a final dry weight concentration. The final dry weight concentration is used to create a correlation between the optical density and the dry weight concentration. A modified Folch method is subsequently used to extract total lipids from the freeze-dried biomass and the extract is assayed for its neutral lipid content using a microplate assay. This assay has been published previously but protocol steps were included here to highlight critical steps in the procedure where errors frequently occur. The bioreactor system described here fills a niche between simple flask cultivation and fully-controlled commercial bioreactors. Even with only 3-4 biological replicates per treatment, our approach to culturing algae leads to tight standard deviations in the growth and lipid assays.

This procedure yields a time course of algal optical density data at OD 550 nm (Figure 4A). The optical density and dry weight concentration data can be correlated (Figure 4B). This is accomplished by first calculating the final dry weight algae concentration after the freeze-drying step. Next, the optical density of the culture serial dilution (performed on the last day of sampling) and the actual dry weight concentrations can b...

Watch this Scientific Journal Video about Cultivation of Green Microalgae in Bubble Column Photobioreactors and an Assay for Neutral Lipids at JoVE.com

Cultivation of Green Microalgae in Bubble Column Photobioreactors and an Assay for Neutral Lipids

Here, we present a protocol to construct lab-scale bubble column photobioreactors and use them to culture microalgae. It also provides a method for the determination of the culture growth rate and neutral lipid content.

There is significant interest in the study of microalgae for engineering applications such as the production of biofuels, high value products, and for the ...

This protocol provides instructions for the construction and use of a Bubble Column Photobioreactor system to grow microalgae, and should be of interest to anyone studying algel biofuels, wastewater treatment, or algel biology. We have found the spire reactor system to produce highly reputable results. The reactor system is also customizable to a wide rang of algae and costs far less than many commercial offerings.Demonstrating the procedure will be Qichen Wang, a graduate student from my laboratory. To begin setup of the Bubble Column Photobioreactors, construct a set of vented lids from the plastic lids of the one liter glass bottles and hybridization tubes as described in the text protocol. Slip a 1/4 inch O ring over the treads of a 1/8th inch panel mount lure fitting, and slide this into the 1/4 inch hole drilled in the lid.Slip a second 1/4 inch over the threads so that the lid is sandwiched between the two O rings. Then slip a lock nut onto the threads and tighten it to fix the panel mount lure in place. Now snap to lock rings onto the exposed male lure, projecting from the lid.Repeat this procedure for each hole in the lid. For lids that will be used on the Bubble Column and bottle reactors, attach 1/8th inch female lure to barb fittings to 1 1/2 inch pieces of 1/8th inch ID PVC tubing. Attach these to each of exposed male lure fittings on the lid.Connect a check valve to the free end of one of the 1/8th inch pieces. Then connect a male lure to barb fitting to the second piece of 1/8th inch tubing projecting from the lid. Click the rotating lock ring into place and fasten a 0.2 micron air filter to this.Compleat assembly of the air deliver system, fish tanks, stir plates, and lights as descried it the text protocol. Concentrate the settled microalgae stock by removing the supernatent by using a vacuum pump. Leave less than 100 milliliters of medium in each bottle, but avoid removing settled algae.Suspend and transfer the algae slurry to sterile 50 milliliter centrifuge tubes. Centrifuge 1, 000 times G for five minutes to further concentrate the algae. In the biosafety cabinet, remove enough supernatent to achieve a total volume of approximately 80 milliliters of algae concentrates for 12 photobioreactors.Avoid vacuuming out the pellet. Transfer the algae concentrate to a steril container. Now, add six milliliters of algae slurry into each photobioreactor with a steril 10 milliliter serological pipette.Swirl the bioreactors to mix algae into the medium. Draw a two milliliter sample from each bioreactor using a serological pipette and transfer to a two milliliter tube. Collect a two milliliter sample every 24 hours to monitor culture progress.Check the sample for ph using test strips and adjust the reactor as needed. Tighten the bioreactor lids and place all bioreactors into the fish tank water bath. Adjust the aeration, carbon dioxide, and lighting to the appropriate levels for the species.Rotate the bioreactor position each day after sampling. Apply 200 microliters of each culture sample in triplicate to wells of a 96 well microplate. Then measure optical density at 550 nanometers and 680 nanometers.Measure a fixed volume of algae culture from each bioreactor with a graduate cylinder and transfer in centrifuge bottles. Centrifuge the culture 4, 696 times G for five minutes. Discard the supernatent by carefully vacuuming it out.Transfer the pellets to labeled 50 milliliter tubes. Rinse the centrifuge bottles with distilled water and transfer the contents to the 50 milliliter tubes. Ensure the total volume does not exceed 45 milliliters.After washing the algae pellets as described in the text protocol, discard the supernatent. Then, add 7.5 milliliters of distilled water to each 50 milliliter tube. Now, vortex the 50 milliliter tubes and transfer the algae slurries into pre weighed 15 milliliter tubes.Rinse the 50 milliliter tubes with additional distilled water, and transfer the liquid to the 15 milliliter tubes keeping the total volume in those tubes to less than 12 milliliters. After centrifuging the 15 milliliter tubes and discarding the supernatent as before, freeze the tubes with pellets at minus 80 degrees Celsius for at least 30 minutes in preparation for freeze drying. Add 1.5 milliliters of folch solvent to each two milliliter tube containing 20 milligrams of freeze dried algae.Pour approximately 0.5 milliliters of zirconia silica beads into each tube until the liquid level reaches two milliliters. Homogenize the algae samples in a bead mill for 20 seconds at a speed of 6.5 meters per second. Transfer the tubes to ices for 30 seconds to chill the samples.Then, repeat five more times to fully extract the lipids. Filter the homogenate through a five milliliter syringe containing a stainless steel wire mesh disc to strain out the beads, collecting filtrate in a 15 milliliter tube. Wash the beads with 1.5 milliliters of folch solvent, pushing liquid through with the syring as necessary.Repeat this wash 2 more times and collect all filtrate in the 15 milliliter tube, yielding a final volume of approximately six milliliters. Add 1.2 milliliters of 0.9%sodium chloride solution to the folch extract in the 15 milliliter tube, and vortex to mix well. Centrifuge the 15 milliliter tubes at 6, 000 times G for five minutes.Record the bottom chloroform phase volume to the nearest 0.1 milliliter using lines on the side of the 15 milliliter tube. Then transfer the bottom phase to a glass vile using a glass pasture pipette. To perform the neutral lipid assay, dilute the lipid extracts and vegetable oil standard three fold with methanol.For each diluted, sample add 80 microliters to a 96 well polypropylene microplate in quadruplicate. For the solvent blank, apply 80 microliters of folch solvent in quadruplicate. For standards, add 10, 30, 60, 90, and 120 microliters of the diluted vegetable oil standard also in quadruplicate.Place the microplate in the fume hood on a preheated dry block heater at 55 degrees Celsius for 20 to 30 minutes until all solvent has evaporated. Remove the microplate from the heating block and let it cool to room temperature. Then, add 30 microliters of isopropyl alcohol to each well and mix by pipetting up and down.Ensure all pipette channels are mixing the solution and resuspending the lipids, yielding a homogenous green liquid. Now, add 200 microliters of one microgram per milliliter a nile red solution to each well, and pipe it up and down 10 times to mix. Following a five minute incubation at room temperature, add 20 microliters of 50%bleach solution to each well, and pipe it up and down five times to mix well.Leave the plat to incubate for 30 minutes at room temperature. After 30 minutes, read the florescence in the samples every five to 10 minutes at 530 nanometers excitation, 575 nanometers emission, with auto cut offs set to 570 nanometers until the signal from the algae samples stabilizes. This procedure yields a time course of algel optical density data at OD 550 nanometers.Control cultures were grown on fresh anate NH4 medium. Treatment one, is co-cultures auxenochlorella protothecoides and azospirillum brasiliense grown on fresh innate NH4 medium. Treatment two, is a azinic A.Protothecoides grown on innate NH4 medium supplemented with 50 milligrams per milliliter IAA, which completely inhibited algae growth.Treatment three, is azinic A.Protothecoides, grown on spent medium from A.Brasilienes. The growth curves show cultures of auxenochlorella protothecoides enter late logarithmic growth at 120 hours. Shown here are corelation curves between the optical density at 550 nanometers and the final dry weight concentration, using a second order polynomial fit.Finally, the coloration can be applied to the time course optical density data to obtain a dry weight growth curve. The same treatments are used here, except that chlorella sorokiniana is cultured instead of auxenochlorella protothecoides. Percent dry weight neutral lipid obtained in the neutral lipid assay correlates well with triose glycerol content on a corresponding thin layer chromatography plate.Unlike A.Protothecoides, the IAA treatment did not inhibit C.Sorkiniana growth. Following lipid extraction of the algae, the remaining cell pallet can be analyzed for its starch and cell wall content, providing a more detailed picture of energy storage products within the cell. The methods described here have enabled new discoveries in the field of algel biofuels and wastewater treatment.Specifically, this system has been used to better understand how bacteria influence algel growth.

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20.4K Views.  Auburn University. This protocol provides instructions for the construction and use of a Bubble Column Photobioreactor system to grow microalgae, and should be of interest to anyone studying algel biofuels, wastewater treatment, or algel biology. We have found the spire reactor system to produce highly reputable results. The reactor system is also customizable to a wide rang of algae and costs far less than many commercial offerings.Demonstrating the procedure will be Qichen Wang, a graduate student from...