Direct discharge of vinasse from the distillery industry causes resource wasting and environmental destruction due to its mass of organic components. Aspergillus oryzae CGMCC5992 is capable of degrading the organic substrates of wastewater. One-factor-at-a-time design was adopted to select the most important nutrients influencing the degradation of organic materials of vinasse. Box–Behnken Design (BBD) with Design-Expert (8.0.4) was used to develop mathematical model equations, study responses, and optimize concentrations of the key nutrients to improve the degradation efficiency. The optimized medium containing 0.3 g/L urea, 20.73 mg/L ZnSO4, and 19.79 mg/L vitamin B6 was supplied to 10-times diluted vinasse; under the optimal condition, a decrease of chemical oxygen demand (COD) from 4,635 to 323 mg/L in vinasse was achieved in 5 days. The reduction of vinasse COD after the optimization of nutrient condition in this study is more significant than those reported previously.

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