Amyris Biotechnologies has raised $24.7 million in equity after offering $62 million worth of shares for sale in July, the company said in a filing with the Securities and Exchange Commission.

The Emeryville, Calif.-based private biofuel developer has engineered yeast that ingest sugar and secrete hydrocarbon, a method that involves fewer steps and possibly cheaper than what its competitors have been able to achieve.

The SEC filing didn't disclose the investors for the latest round. We've emailed the company for more information.

The company had previously raised $120 million from investors including DAG Ventures, Khosla Ventures, Kleiner Perkins Caufield & Byers and TPG Ventures.

Amyris opened a pilot production plant at its headquarters last November, when CEO John Melo touted the startup's ability to produce a form of diesel that it could sell for $2 per gallon or less. That was about how much conventional fossil diesel would cost (see Amyris: Were Better Than Biodiesel, Ethanol or Gas).

The company also is developing jet fuel and chemicals that could replace those that rely on petroleum as the raw material.

Amyris hopes to build commercial plants and sell its fuels and chemicals from those facilities starting in 2011.

In June this year, Amyris opened a demonstration plant in Brazil to take advantage of the abundant sugarcane supply as feedstock.

The path to producing biofuels typically involves two processes: converting plants or some sort of biomass into sugar, and then feed the sugar to microbes, algae or other organisms for fuel making.

The second process typically yields lipids or chemical compounds that require further refining to become commercial products.

Amyris' yeast skips that refining step and secretes hydrocarbon as a direct hydrocarbon replacement. Its key competitors include Mascoma in Lebanon, N.H., and LS9 in South San Francisco, both of which also claim to have devised a simpler and more cost effective way to produce fuels.

Some startups have opted to skip the use of sugar all together. Joule Biotechnologies in Cambridge, Mass., came out of stealth mode last month to provide a glimpse of its technology.

Joule has developed organisms that thrive under sunlight and in tanks filled with carbon dioxide, and they could secrete hydrocarbon or ethanol (see Joule Biotech: Does It Have the Superbug for Biofuel?). One of Joule's founders, David Berry of Flagship Ventures also co-founded LS9.

Image via Amyris Biotechnologies.