Monday, June 27, 2011

Boosting Photosynthesis to Boost Feedstock Production

Research finds the efficiency of photosynthesis could be improved by synthetic biology, using solar power technologies as a template, which could be valuable for boosting crop yields.

The National Renewable Energy Laboratory (NREL) reported in Science that lessons learned in the course of photovoltaic research could be used to make photosynthesis more efficient and in turn, increase the productivity of crops. In the paper, titled Comparing Photosynthetic and Photovoltaic Efficiencies and Recognizing the Potential for Improvement,” researchers conclude that under optimal conditions PV is 30% more efficient than photosynthesis, as more energy is consumed in photosynthesis to synthesize biomass. They theorize that it is possible to use common principles between the two areas of inquiry to produce both more efficient photovoltaics (for higher efficiencies in energy production) and more efficient cellular machinery for photosynthesis (resulting in more energy-dense crops). This could be done by expanding the range of light that can be absorbed by plants; naturally they only absorb a narrow range of light frequencies at the blue end of the spectrum. However, with synthetic biology this could be expanded to absorb light from across the spectrum, as is often the case in advanced solar cells. Also, if the mechanism of photosynthesis was mapped to identify inefficient parts, synthetic biology could be used to optimize them. This could be done to produce plants that convert light into usable energy with efficiency comparable to the best solar cells on the market.

Michigan State University Professor of Photosynthesis and Bioenergetics, David Kramer:
“This is critical since it’s the process that powers all of life in our ecosystem. The efficiency of photosynthesis, and our ability to improve it, is critical to whether the entire biofuels industry is viable.”
“Plants are less efficient at capturing the energy in sunlight than solar cells mostly because they have too much evolutionary baggage. Plants have to power a living thing, whereas solar cells only have to send electricity down a wire. This is a big difference because if photosynthesis makes a mistake, it makes toxic byproducts that kill the organism. Photosynthesis has to be conservative to avoid killing the organisms it powers.”

Professor Kramer’s own research suggests that replacing some of the photosynthetic machinery of the plant cell with that of a certain species of cyanobacteria could widen the range of light frequencies that can be converted into usable sugars. This would be ambitious, but a more easily achievable prospect in the near-term than a ground-up redesign.


Many genetic modifications developed for increasing crop yields do so by making the crop resistant to something which decreases the yield (such as drought or pests) rather than a modification which is aimed at increasing the growth of the plant in general. GM technology often involves “stacking” traits; a crop might be pesticide resistant, herbicide resistant and drought tolerant and optimised photosynthesis mechanisms would be a useful trait to stack with other common modifications to further increase the productivity of these crops. It could also be argued that optimized photosynthesis would be a “cleaner” modification than some common modifications; for example herbicide resistant crops which result in greater herbicide use which in turn has a negative environmental impact.

Regulatory hurdles for such crops will have to be overcome for this ambitious project to bear fruit. For example, in the EU there is a requirement for products with more than 0.9% GM material to be labelled, necessitating analytical methods which are capable of quantifying the amount of GM material in a sample which recognizes this new modification.

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