The nutritional medium requirement for biosurfactant production by Bacillus licheniformis K51 was optimized. The important medium components, identified by the initial screening method of Plackett-Burman, were $H_3PO_4,;CaCl_2,H_3BO_3$, and Na-EDTA. Box-Behnken response surface methodology was applied to further optimize biosurfactant production. The optimal concentrations for higher production of biosurfactants were (g/l): glucose, $1.1;NaNO_3,;4.4;MgSO_4{cdot}7H_2O,;0.8;KCl,;0.4;CaCl_2,;0.27;H_3PO_4,;1.0ml/l;;and;trace elements;(mg/l):H_3BO_3,;0.25;CuSO_4,;0.6;MnSO_4,;2.2;Na_{2}MoO_4,;0.5;ZnSO_4,;6.0;FeSO_4,;8.0;CoCL_2,;1.0;$ and Na-EDTA, 30.0. Using this statistical optimization method, the relative biosurfactant yield as critical micelle dilution (CMD) was increased from $10{ imes};to;105{ imes}$, which is ten times higher than the non-optimized rich medium.