Brookhaven researchers Jilian Fan, Changcheng Xu, and Chengshi Yan with cultures of algae that were shown to increase oil production in response to excess carbon.

(Phys.org) -- Overturning two long-held misconceptions about oil production in algae, scientists at the U.S. Department of Energys Brookhaven National Laboratory show that ramping up the microbes overall metabolism by feeding them more carbon increases oil production as the organisms continue to grow. The findings published online in the journal Plant and Cell Physiology on May 28, 2012 may point to new ways to turn photosynthetic green algae into tiny green factories for producing raw materials for alternative fuels.

We are interested in algae because they grow very quickly and can efficiently convert carbon dioxide into carbon-chain molecules like starch and oils, said Brookhaven biologist Changcheng Xu, the papers lead author. With eight times the energy density of starch, algal oil in particular could be an ideal raw material for making biodiesel and other renewable fuels.

But there have been some problems turning microscopic algae into oil producing factories.

For one thing, when the tiny microbes take in carbon dioxide for photosynthesis, they preferentially convert the carbon into starch rather than oils. Normally, algae produce very little oil, Xu said.

Before the current research, the only way scientists knew to tip the balance in favor of oil production was to starve the algae of certain key nutrients, like nitrogen. Oil output would increase, but the algae would stop growing not ideal conditions for continuous production.

Another issue was that scientists didnt know much about the details of oil biochemistry in algae. Much of what we thought we knew was inferred from studies performed on higher plants, said Brookhaven biochemist John Shanklin, a co-author whos conducted extensive research on plant oil production. Recent studies have hinted at big differences between the microbial algae and their more complex photosynthetic relatives.

Enlarge

Confocal image of the algae Chlamydomonas showing the accumulation of oil droplets (golden dots). Red represents chlorophyll autofluorescence.

The scientists grew cultures of Chlamydomonas reinhardtii the fruit fly of algae under a variety of nutrient conditions, with and without inhibitors that would limit specific biochemical pathways. They also studied a mutant Chlamydomonas that lacks the capacity to make starch. By comparing how much oil accumulated over time in the two strains across the various conditions, they were able to learn why carbon preferentially partitions into starch rather than oil, and how to affect the process.

See original here:
Carbon is key for getting algae to pump out more oil