Qteros, a US-based developer of biofuels previously backed by oil groups BP and Valero Energy, has raised $22m in its initial series C round.
No investors were disclosed in this round, although beyond the two oil groups as previous investors have been venture capital firms Battery Ventures, Venrock, Soros Fund Management, Long River Ventures and Camros Capital.
John McCarthy, executive president of Qteros since the start of the last year, said: "As we continue to accelerate our commercial plans, which now include our recently announced strategic partnership with Praj Industries, I would expect to continue discussions with a select group of strategic and financial investors who have expressed strong interest in supporting our efforts."
The strategic partnership with India’s Praj Industries will accelerate commercialization efforts for industrial-scale cellulosic ethanol production.
Qteros, formerly known as SunEthanol, raised $25m in its series B round in November 2008, a year after its first regulatory filing.