Sophorolipids (SLs) are amphiphilic compounds produced from a variety of saccharides and vegetable oils by the yeast Starmerella bombicola and related strains, and they have commercial uses as detergents. In the present study, SL production was investigated using a corncob hydrolysate (CCH) medium derived from lignocellulosic feedstocks as a source of hydrophilic carbon substrates. Excess sulfuric acid concentrations during pretreatment of the corncobs increased the furfural concentrations and turned the CCH dark brown. The optimal sulfuric acid concentration was 1% (w/v), and the treated CCH, containing 45 g/I glucose, allowed the production of 33.7 g/I of SLs following 4 days of cultivation. Additional autoclaving (121 degrees C, 20 min) inhibited SL production and cell growth by 36% and 40%, respectively. Ammonium nitrate (0.1 g-N/I) restored SL production to the autoclaved CCH. Finally, a cost-effective SL production of 49.2 g/I, with a volumetric productivity of 12.3 g/I/day, was achieved using CCH medium during batch cultivation in ajar fermentor. (C) 2014, The Society for Biotechnology, japan. All rights reserved.