Production of Biofuels in Eukaryotic Algae

Algae offer the potential to produce liquid biofuels at a scale and cost that can be competitive with existing fossil fuel production, and biofuel production from algae will not compete with food crops for arable land use. However, if we are to realize biofuel production from algae in a time frame that coincides with our national needs, we need to immediately begin the development of the molecular and genetic tools that will allow algae to become an economically viable biofuel source. We also need to train the young scientists whose work will be essential to achieving the production of energy from renewable sources. A key focus of work in my lab is to develop molecular genetic tools in algal while training graduate students and post-doctoral fellows in algal genetics and recombinant technologies, all of which will be essential expertise for producing algae-derived biofuels on a large scale.

With fossil fuel reserves dwindling, mandates requiring the reduction of CO2 emissions, and a need for national energy independence, we face the formidable challenge of developing sustainable forms of carbon-neutral energy in an economically viable manner. Among these new energy forms will surely be biofuels, fuels derived from organisms that capture solar energy for conversion into useable forms of fuel. Two first generation biofuels, ethanol, made by fermenting corn or sugar cane, and biodiesel, made from vegetable oils are already sold in the US. However, the row crops used to produce these biofuels compete with food production and require large amounts of arable land, water and fertilizer, making them less than ideal sources of biofuel. Recently, attention has turned to a promising alternative: single-celled algae. Algae grow quickly, need few added nutrients, and get their energy from sunlight. They can be grown at a very large scale and take CO2 from the air as part of their growth process. Compared with crops normally used to produce vegetable oil such as soybeans or palm, algae can produce 30 times the amount of oil per acre [1]. The US Department of Energy’s Aquatic Species Program - Biodiesel from Algae” highlighted a number of advantages of using algae as a source of biofuels and summarized their finding with the statement “Put quite simply, microalgae are remarkable and efficient biological factories capable of taking a waste (zero-energy) form of carbon (CO2) and converting it into a high density liquid form of energy (natural oil)” [1]. Clearly, algae hold enormous promise to become a major source of renewable energy, especially as transportation fuels, and one that makes sense both economically and environmentally. The challenge in realizing the potential of algae as a biofuel source lies in our relatively limited knowledge of algal physiology and genetics. By developing state of the art molecular genetics tools, and by continuing to develop algal culturing technologies, we hope to optimize algae to be an efficient and economical source of biofuel.

To date, molecular genetic tools have been developed for only a few algae, including the green algae Chlamydomonas reinhardtii, and the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. Among these, only C. reinhardtii has well established systems for recombinant protein expression from both the nuclear and chloroplast genomes, and even in this species only a handful of recombinant proteins have been expressed to any appreciable level [2]. Importantly, we have recently been able to demonstrate that C. reinhardtii can be engineered to produce novel hydrocarbon molecules that are superior biofuels, demonstrating the potential of microalgae as a biofuel source. We are developing molecular genetic tools to allow for robust recombinant protein expression in algae, and to engineer algae for the production of biofuel molecules.

1. Sheehan, J., Dunahay, T., Benemann, J., Roessler, P. (1998) A Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae; Close-Out Report. U.S. Department of Energy.
2. Mayfield, S.P., et al., Chlamydomonas reinhardtii chloroplasts as protein factories. Curr Opin Biotechnol, 2007. 18(2): p. 126-33.