Virent Energy Systems is ready to rev up hiring and research and move closer to selling its biofuel to the public now that investors have pumped another $46.4 million into the Madison company. Virent converts plant sugars from beets, corn and sugar cane into fuel that has the same molecular structure as gasoline; it would be blended with petroleum-based gas for up to a 50/50 mixture. Eventually, the company wants to use non-food agricultural residues for its biofuel. With the latest funding round, Virent has attracted more than $116 million since the company was founded in 2002, based on UW-Madison research.