High-cell-density cultivation of oleaginous yeast Cryptococcus curvatus for biodiesel production using organic waste from the brewery industry

► Spent yeast was used to cultivate an oleaginous yeast Cryptococcus curvatus. ► Spent yeast, without any pretreatment, could serve as complete nutrients. ► The highest lipid production was achieved at C/N ratio of 35 in stepwise cultivation. ► Lipid from C. curvatus was quality sufficient to be converted into a transport fuel. ► Utilization of spent yeast can greatly reduce the cost of biodiesel production.