Microalgae are single-celled organisms that, like green plants, use photosynthesis to capture carbon dioxide and turn it into complex compounds, including oils and lipids. Marine algae species can be raised in saltwater ponds and so do not compete with food crops for land or fresh water.
"They can live in saltwater, they take sunlight and carbon dioxide as a building block, and make these long chains of oil that can be converted to biodiesel," said Annaliese Franz, assistant professor of chemistry and an author of the paper.
Franz, graduate students Megan Danielewicz, Diana Wong and Lisa Anderson, and undergraduate student Jordan Boothe screened 83 compounds for their effects on growth and oil production in four strains of microalgae. They identified several that could boost oil production by up to 85 percent, without decreasing growth.
Among the promising compounds were common antioxidants such as epigallocatechin gallate, found in green tea, and butylated hydroxyanisole (BHA), a common food preservative.
The team has carried out growth experiments in culture volumes of up to half a liter. They calculate that some of the chemicals they analyzed would be cost-effective when scaled up to a 50,000 liter pond. After oils have been extracted from the algae, the remaining mass can be processed for animal feed or other uses.
Franz came to UC Davis in 2007 with a background in pharmaceutical chemistry. Given the campus's emphasis on biofuels, she started thinking about applying high-throughput techniques used to screen for new drugs to looking for compounds that could affect microalgae.
The idea, Franz said, is to look for small molecules that can affect a metabolic pathway in a cell. By setting up large numbers of cell cultures and measuring a simple readout in each, it's possible to screen for large numbers of different compounds in a short time and home in on the most promising.
"The basic concept comes from the pharmaceutical industry, and it's been used for human cells, plants, yeast, but not so far for algae," she said.
"There are many cases where small molecules are having an effect to treat a disease, so it makes sense that if you can affect a pathway in a human for a disease, you can affect a pathway in an algal cell," Franz said.