Regardless of current market conditions and availability of conventional petroleum sources, alternatives are needed to circumvent future economic and environmental impacts from continued exploration and harvesting of conventional hydrocarbons. Diatoms and green algae (microalgae) are eukaryotic photoautotrophs that can utilize inorganic carbon (e.g., CO2) as a carbon source and sunlight as an energy source, and many microalgae can store carbon and energy in the form of neutral lipids. In addition to accumulating useful precursors for biofuels and chemical feed stocks, the use of autotrophic microorganisms can further contribute to reduced CO2 emissions through utilization of atmospheric CO2. Because of the inherent connection between carbon, nitrogen, and phosphorus in biological systems, macronutrient deprivation has been proven to significantly enhance lipid accumulation in different diatom and algae species. However, much work is needed to understand the link between carbon, nitrogen, and phosphorus in controlling resource allocation at different levels of biological resolution (cellular versus ecological). An improved understanding of the relationship between the effects of N, P, and micronutrient availability on carbon resource allocation (cell growth versus lipid storage) in microalgae is needed in conjunction with life cycle analysis. This mini-review will briefly discuss the current literature on the use of nutrient deprivation and other conditions to control and optimize microalgal growth in the context of cell and lipid accumulation for scale-up processes.
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Acknowledgments The authors would like to thank all members of the MSU Algal Biofuels Group for their helpful discussions. Support was provided by the US Department of Energy-Advancements in Sustainable Algal Production (ASAP) program under contract DE-EE0005993 and the National Science Foundation Sustainable Energy Pathways (SEP) Program under NSF CHE-1230632. We also would like to acknowledge student support from the Molecular Biosciences Program at Montana State University and the NSF IGERT Program in Geobiological Systems (DGE 0654336).
- Algal biofilm
- Biofuel ecology