Charles Darwin's 200th birthday arrives on February 12, 2009, and while his theory of evolution has stood the test of two centuries, scientists at the University of California, Berkeley, are now are working to circumvent evolution, at least a bit, by introducing some non-accidental changes into the tiniest of all plants.
The scientists want to genetically modify microalgae so as to minimize the number of chlorophyll molecules the algae need to harvest light without compromising the photosynthesis process in the cells. The goal is to use the microalgae for making bio-fuel. Instead of making more sugar molecules for themselves, they could be producing hydrogen or hydrocarbons for us, and in the process mitigate the threat of climate change caused by the burning of fossil fuels.
The Berkeley researchers have identified the genetic instructions in the algae genome responsible for deploying about 600 chlorophyll molecules in the cell’s light-gathering antennae. They figure that the algae can get along with only about 130 molecules.
Why go to this trouble? Researcher Tasios Melis argues that a larger chlorophyll antenna helps the organism compete for sunlight absorption and survive in the wild, where sunlight is often limited but is detrimental to the engineering-driven effort of using algae to convert sunlight into biofuel. The scientists want to divert the normal function of photosynthesis from generating biomass to making products such as lipids, hydrocarbons, and hydrogen.
Microalgae are ideal because of their high rate of photosynthesis; perhaps ten times more efficient than land plants such as sugarcane, maize, and switchgrass, which are often discussed as possible bio-fuel stocks.
Besides getting the algae to convert more sunlight to fuel, another issue that needs to be addressed is how to configure bio-culture tanks in such a way that sunlight can penetrate the outer layer of algae so that lower-down layers can also participate in the photo-conversion. Melis calls the overall effort to maximize the efficiency of the solar-to-product conversion process with microalgae, “cellular optics.”
How soon can algae play a role? “Progress is substantial to date, but not enough to make the process commercially competitive with fossil fuels,” Melis said. “Further improvement in the performance of photosynthesis under mass culture conditions, and in the yield of ‘biofuels’ by the microalgae are needed before cost parity with traditional fuels can be achieved.”
The new results were reported in a recent meeting of the Optical Society of America.
(Phillip F. Schewe)