Biorefineries typically release about one third of the carbohydrate carbon as carbon dioxide (CO2) during fermentation. Ideally, a photosynthetic microorganism could be engineered to convert CO2 directly into liquid transportation fuels. Unfortunately, current approaches for using photosynthetic microorganisms to make fuel from CO2 suffer from many technical challenges, including the need to harvest cells, extract the energy-dense oils, and then convert the oil into the final product. To address these challenges, the proposed research will genetically engineer two cyanobacteria (Anabaena sp. PCC7120 and Nostoc punctiforme) to directly produce and secrete linalool, a ten-carbon terpene alcohol, through the non melavonate (MEP) pathway using sunlight as the energy source and CO2 as the carbon feedstock. To intensify linalool production, efforts will also be made to genetically engineer the cyanobacteria to increase the rate of photosynthetic CO2 fixation, and to re-direct the carbon flow to linalool synthesis by shutting unnecessary pathways that compete for fixed carbon. Towards this end, the proposed research plan has three components: 1) stable insertion of optimal LinS gene into chromosome of cyanobacteria; 2) correct metabolic flux to maximize linalool productivity; 3) assess linalool production under both photosynthetic and heterotrophic conditions. The performance of the engineered strains will be assessed in a recirculating photobioreactor system that uses phase separation for linalool recovery. Linalool yield and productivity will be compared to input requirements.
Broader Impacts
The proposed education and outreach activities will focus on providing opportunities for Native American students through the 2+2+2 Program at the South Dakota State University (SDSU). First, week-long activities in metabolic engineering will be developed as part of the summer institute program. Through these activities, Native American high school students and their teachers will be recruited to participate in 6-8 week long, summer research internships. Teachers will use the research experience to develop classroom/lab activities to share with their students. Students will participate in on-going projects, and then will be given the opportunity to present their efforts at scientific meetings organized through the South Dakota Academy of Science and SDSU?s Undergraduate Research Day. Native American undergraduate students who attend tribal colleges and then transfer to SDSU will also be offered summer research experiences.
