Perhaps inspired by Arizona’s blazing summers, Arizona State University scientists have developed a new method that relies on heat to improve the yield and lower the costs of high-energy biofuels production, making renewable energy production more of an everyday reality.

ASU has been at the forefront of algal research for renewable energy production. Since 2007, with support from federal, state and industry funding, ASU has spearheaded several projects that utilize photosynthetic microbes, called cyanobacteria, as a potential new source of renewable, carbon-neutral fuels. Efforts have focused on developing cyanobacteria as a feedstock for biodiesel production, as well as benchtop and large-scale photobioreactors to optimize growth and production.

ASU Biodesign Institute researcher Roy Curtiss, a microbiologist who uses genetic engineering of bacteria to develop new vaccines, has adapted a similar approach to make better biofuel-producing cyanobacteria.

"We keep trying to reach ever deeper into our genetic bag of tricks and optimize bacterial metabolic engineering to develop an economically viable, truly green route for biofuel production,” said Roy Curtiss, director of the Biodesign Institute's Centers for Infectious Diseases and Vaccinology and Microbial Genetic Engineering as well as professor in the School of Life Sciences.

Cyanobacteria are like plants, dependent upon renewable ingredients including sunlight, carbon dioxide and water that, through genetic engineering, can be altered to favor biodiesel production. Cyanobacteria offer attractive advantages over the use of plants like corn or switchgrass, producing many times the energy yield with energy input from the sun and without the necessity of taking arable cropland out of production.

Colleague Xinyao Liu and Curtiss have spent the last few years modifying these microbes.  Their goal is to bypass costly processing steps (such as cell disruption, filtration) for optimal cyanobacterial biofuel production.

“We wanted to develop strains of cyanobacteria that basically can process themselves,” said Curtiss. “A couple of years ago, we developed a Green Recovery process that is triggered by removing carbon dioxide to control the synthesis of enzymes, called lipases, that degrade the cell membranes and release the microbes’ precious cargo of free fatty acids that can be converted to biofuels,”

However, when growth of cyanobacteria is scaled up to meet industrial needs, they become dense, and the self-shading that occurs in concentrated cultures, does not let in enough light to produce enough of the lipases to efficiently drive the process. Thus the original Green Recovery was light dependent and maximally efficient at sub-optimal culture densities.