Degradation of aflatoxin B-1 in groundnut cake, a residue after oil extraction, by Rhodococcus erythropolis was optimized using response surface methodology. The bacterium was first grown in synthetic medium to determine optimal growth conditions using the combination of the Plackett-Burman and Box-Behnken methods and consequently aflatoxin B-1 in groundnut cake slurry was degraded under varying culture conditions. Optimal growth conditions were found as 22.5 A degrees C of temperature, pH 7, 100 mL of culture volume in 500 mL flasks, 1 % (v/v) of inoculum size, 135 rpm of agitation speed, 5 g/L of glucose and 5 g/L of peptone concentration according to analysis of the Box-Behnken design. Optimal detoxification conditions were found as 27.4 % (w/v) of solid concentration, 4.88 % (v/v) of inoculum size and 24 h of incubation time by Box-Behnken response surface optimization. Maximum detoxification level was predicted as 92.2 % by the constructed model while the experimental counterpart was 87.3 %. The suggested culture conditions have the potential to decrease aflatoxin B-1 from 200 mu g/kg to below 20 mu g/kg, the regulatory limit, in feed materials. Further studies are needed to test the obtained results at a larger scale and to finalize safety assessment of the final product by animal testing.