Algal Oils – Report 1
Algal oil production for use as fuel can have a global impact on fossil fuel consumption and emissions. Algae are a resource that can easily be renewed and sustained in a variety of conditions; they have very high growth rates and can yield more oil per acre than other plant based oils (Fang, 2014). Additionally, RNA technology and bioprocesses enable exaggerated fuel growth from algae organisms. Therefore algae-based biodiesel fuel has the potential to be a more economical and environmental solution to a growing energy demand. The biggest, most immediate, application of algae oil fuel would be energy for the transportation sector – as algae biodiesel could be easily implemented in existing transportation energy infrastructure (ExxonMobil, 2018).
There are many companies who have entered the algae oil industry over the last decade. An unexhaustive list includes Sapphire Energy, Chevron Corporation, Shell (in conjunction with Cellana), and Exxon Mobile (in conjunction with Synthetic Genomics) (Wesoff, 2017). The U.S. Department of Energy offers subsidies to many companies who invest in researching and producing algal based fuels.
The oil is naturally produced in algae species – particularly Chlamydomonous reinhardtii and Nannochloropis. Both species are green microalgae species that require nitrogen to grow. Lipid production of algae can be increased through genetic manipulation of the enzymes and promoters that control fatty acid (TAG) production (Radakovits et. al., 2010).
https://www-sciencedirect-com.proxy.lib.ohio-state.edu/science/article/pii/B9780444595584000036The current market size for algae oils, particularly to be used as fuels, is very small. Industries have not made these oils economically practical to begin sustained large-scale production. Only five percent of transportation energy comes from biomass fuel – almost all of which is corn-based ethanol. However, the future outlook of the energy sector, taking into consideration the depletion of nonrenewable resources, suggests algae oil could be a major global market. Petroleum currently accounts for 36.2 percent of energy consumption in the U.S. (Desjardins, 2018). But this percentage is not sustainable in the long term. Efforts to use corn based biomass as fuel also conflicts with food production and arable land requirements. If oils from algae could complete economically with current means of energy production, it could meet the demands for the majority of the transportation energy sector: 28.1% of U.S. energy consumption. Production size could withstand high demands due to algae’s dense population growth and limited resource requirements.
-2286001333500http://www.visualcapitalist.com/visualizing-u-s-energy-consumption-one-chart/There are three primary methods for producing algal oils (or rather, increasing the yield of oils produced naturally). The first includes stimulating the enzyme Acetyl CoA carboxylase – the enzyme used in the first committed step of TAG synthesis in algae. This is achieved by introducing citrate, a derivative of citric acid, to the algae species (Berg et. al., 2002). Citrate binds to ACCase and allosterically controls fatty acid synthesis by interrupting inhibition pathways regulated by phosphorylation. A common issue with this process, and algal oil production in general, is the induced nutrient starvation required to start oil production in algae. Removing key nutrients like phosphorus and nitrogen promote the production of oils but also reduces growth rate. This is counterproductive to large scale processing. However, the second method of producing algal oils can offer a solution: Researchers have found that microalgae Nannochloropsis maintains growth rates under nutrient deprivation better than counterpart species. They also discovered genes and promoters from Chlamydomonous reinhardtii could be inserted into Nannochloropsis to overproduce oils during phosphorous starvation. This is done by placing enzyme CrDGTT4 from C. reinhardtii and its promoter gene SQD2 into Nannochlropsis (Iwai M. et. al., 2015). This ultimately overproduces oils in Nannochloropopsis while maintaining other functions despite phosphorous deprivation. The last method of producing oils involves DNA plasmids. Plasmid form DNA has been found in some algae species, particularly red algae, enabling the advantages of RNA technology in engineering the overproduction of oil. This is experimentally replicated by constructing plasmid pMSD1 (consisting of accA, accB, accC, and accD genes) to code for the production of ACCase subunits to overexpress Acetyl CoA Carboxylase activity (Davis et. al., 2000). As discussed earlier, this is a key enzyme in fatty acid biosynthesis.
Berg, Jeremy. Et. al . Acetyl Coenzyme A Carboxylase Plays a Key Role in Controlling Fatty Acid Metabolism. Biochemistry 5th Edition Sec 22.5. National Center for Biotechnology Information. 2002.
Davis, Mark. Et. al. Overproduction of Acetyl-CoA Carboxylase Activity Increases the Role of Fatty Acid Biosynthesis in Escherichia coli. University of Illinois. Journal of Biological Chemistry. 275. Pg 28593-28598. 2000.
Desjardins, Jeff. Visualizing U.S. Energy Consumption in One Chart. Visual Capitalist. 2018.
ExxonMobil. Advanced Biofuels and Algae Research. 2018.
Fang, So-Chiung. Metabolic Engineering and Molecular Biotechnology of Microalgae for Fuel Production. Elsevier. Biofuel from Algae. Pg 47-65. 2017.
Iwai, M. et. al. Genetic Manipulation for Algal Biofuel Production. Tokyo Institute of Technology. 2015.
Radakavits, Randor. Et. al. Genetic Engineering of Algae for Enhanced Biofuel Production. American Society for Microbiology. Eukaryotic Cell. Pg 486-501. 2010.
Wesoff, Eric. Hard Lessons From the Great Algae Biofuel Bubble. Green Tech Media. 2017.