Assessment of Nannochloropsis gaditana growth and lipid accumulation with increased inorganic carbon delivery
Algal biomass refineries for sustainable transportation fuels, in particular biodiesel, will benefit from algal strain enhancements to improve biomass and lipid productivity. Specifically, the supply of inorganic carbon to microalgal cultures represents an area of great interest due to the potential for improved growth of microalgae and the possibility for incorporation with CO2 mitigation processes. Combinations of bicarbonate (HCO3−) salt addition and application of CO2 to control pH have shown compelling increases in growth rate and lipid productivity of fresh water algae. Here, focus was placed on the marine organism, Nannochloropsis gaditana, to investigate growth and lipid accumulation under various strategies of enhanced inorganic carbon supply. Three gas application strategies were investigated: continuous sparging of atmospheric air, continuous sparging of 5% CO2 during light hours until nitrogen depletion, and continuous sparging of atmospheric air supplemented with 5% CO2 for pH control between 8.0 and 8.3. These gas sparging schemes were combined with addition of low concentrations (5 mM) of sodium bicarbonate at inoculation and high concentration (50 mM) of sodium bicarbonate amendments just prior to nitrogen depletion. The optimum scenario observed for growth of N. gaditana under these inorganic carbon conditions was controlling pH with 5% CO2 on demand, which increased both growth rate and lipid accumulation. Fatty acid methyl esters were primarily comprised of C16:0 (palmitic) and C16:1 (palmitoleic) aliphatic chains. Additionally, the use of high concentration (50 mM) of bicarbonate amendments further improved lipid content (up to 48.6%) under nitrogen deplete conditions when paired with pH-controlled strategies.
KeywordsMicroalgae Fatty acid methyl ester (FAME) Nannochloropsis gaditana Inorganic carbon Nitrogen limitation Chlorophyll
A special thank you to all members of the MSU Algal Biofuels Group for their introspective discourse on algal biofuel-related topics.
A portion of this research was supported by the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Biomass Program under Contract No. DE-EE0005993. Support for TCP was also provided by Church and Dwight Co., Inc. Instrumental support was provided through the Environmental and Biofilm Mass Spectrometry Facility at the College of Engineering (COE), and the Center for Biofilm Engineering (CBE), at Montana State University (MSU).
Compliance with ethical standards
A patent entitled “Bicarbonate Trigger for Inducing Lipid Accumulation in Algal Systems” (Pat. No 9,096,875) was co-authored by contributing authors Robert D. Gardner and Brent M. Peyton.
- Fields MW, Hise A, Lohman EJ, Bell T, Gardner RD, Corredor L, Moll K, Peyton BM, Characklis GW, Gerlach R (2014) Sources and resources: importance of nutrients, resource allocation, and ecology in microalgal cultivation for lipid accumulation. Appl Microbiol Biotechnol 98:4805–4816CrossRefPubMedPubMedCentralGoogle Scholar
- Gardner RD, Cooksey KE, Mus F, Macur R, Moll K, Eustance E, Carlson RP, Gerlach R, Fields MW, Peyton BM (2012) Use of sodium bicarbonate to stimulate triacylglycerol accumulation in the chlorophyte Scenedesmus sp and the diatom Phaeodactylum tricornutum. J Appl Phycol 24:1311–1320CrossRefGoogle Scholar
- Guihéneuf F, Stengel DB (2013) LC-PUFA-enriched oil production by microalgae: accumulation of lipid and triacylglycerols containing n-3 LC-PUFA is triggered by nitrogen limitation and inorganic carbon availability in the marine haptophyte Pavlova lutheri. Mar Drugs 11:4246–4266CrossRefPubMedPubMedCentralGoogle Scholar
- Hallenbeck PC, Grogger M, Mraz M, Veverka D (2015) The use of Design of Experiments and Response Surface Methodology to optimize biomass and lipid production by the oleaginous marine green alga, Nannochloropsis gaditana in response to light intensity, inoculum size and CO2. Bioresour Technol 184:161–168CrossRefPubMedGoogle Scholar
- Radakovits R, Jinkerson RE, Fuerstenberg SI, Tae H, Settlage RE, Boore JL, Posewitz MC (2012) Draft genome sequence and genetic transformation of the oleaginous alga Nannochloropis gaditana. Nat Commun 3:686. Google Scholar
- Simionato D, Block MA, La Rocca N, Jouhet J, Maréchal E, Finazzi G, Morosinotto T (2013) The response of Nannochloropsis gaditana to nitrogen starvation includes de novo biosynthesis of triacylglycerols, a decrease of chloroplast galactolipids, and reorganization of the photosynthetic apparatus. Eukaryot Cell 12:665–676CrossRefPubMedPubMedCentralGoogle Scholar