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/l glucose, allowed the production of 33.7 g/l of SLs following 4 days of cultivation. Additional
autoclaving (121C, 20 min) inhibited SL production and cell growth by 36% and 40%, respectively. Ammonium
nitrate (0.1 g-N/l) restored SL production to the autoclaved CCH. Finally, a cost-effective SL production of 49.2 g/l, with a
volumetric productivity of 12.3 g/l/day, was achieved using CCH medium during batch cultivation in a jar fermentor.