Rhodococcus opacus DSM 1069 utilized pine organosolv Pretreatment effluent as a sole carbon and energy source for 120 h at 1.5 w/v% solids concentration and accumulated a maximum of 26.99 +/- 2.88% of its cellular dry weight in oils composed of oleic, palmitic, and stearic fatty acids. These results establish the potential for lignocellulosic pretreatment effluent as a feedstock for microbial biodiesel production via oleaginous R. opacus and an interesting route for biorefinery waste stream optimization. (C) 2014 Elsevier Ltd. All rights reserved.