Algal biofuels represent a renewable, potentially viable, solution to mitigate transportation fuel demands. A novel diatom strain, RGd-1, isolated from Yellowstone National Park, produces high concentrations of lipids that can be converted to biodiesel. To increase the cell concentration and determine optimal conditions for growth, RGd-1 was grown without added Si, in the presence of four Si concentrations within the soluble range (0.5-2mM), and one above the soluble range (2.5mM). Medium Si concentrations and intracellular triacylglycerol (TAG) content were monitored daily by inductively coupled plasma mass spectrometry and Nile Red fluorescence, respectively (end-point TAG values were measured using gas chromatography). Si depletion with or without combined nitrate (NO3-) limitation was shown to induce TAG accumulation. Additionally, the effects of sodium bicarbonate (NaHCO3) supplementation were examined on cultures grown using two NO3- concentrations (2.94 and 1mM NO3-), which also resulted in increased TAG accumulation. It was determined that utilizing a combination of two independent physiological stresses and HCO3- supplementation resulted in the highest total and per cell TAG accumulation.
Bibliographical noteFunding Information:
The authors would like to thank all members of the MSU Algal Biofuels Group. Additionally, the authors especially thank John Barnick and Ellen Lauchnor for their help with running the ICP-MS, Ann Willis at the CBE for assistance in running IC, as well as Hannah Newhouse and Dan McDonald for assisting with clone libraries and Nate Murphy for experimental support. The authors acknowledge Yellowstone National Park as well as funding for the establishment and operation of the Environmental and Biofilm Mass Spectrometry Facility at Montana State University (MSU) through the Defense University Research Instrumentation Program (DURIP, Contract Number: W911NF0510255) and the MSU Thermal Biology Institute from the NASA Exobiology Program (Project NAG5-8807). Funding Sources: U.S. Department of Energy : Office of Biomass Programs grant DE-FG36-08G018161 , Office of Energy Efficiency and Renewable Energy (EERE) Biomass Program under Contract No. DE-EE0003136 and National Science Foundation CHE-1230632 . This work was additionally made possible by Betsy Pitts and the microscopy facilities at the Center for Biofilm Engineering, which was supported by funding obtained from the NSF-MRI Program and the M.J. Murdock Charitable Trust .
© 2014 Elsevier B.V.
- Sodium bicarbonate