A Plackett-Burman design was conducted for the selection of 8 metabolites in the liquid submerged fermentation process for gibberellin acid, aimed to improve the productivity of gibberellin acid by Gibberella fujikuroi. The results showed that oxalacetate, calcium gluconate and vitamin B2 had great influence on the yield of gibberellin acid. The optimal composition of the additive amount was approached gradually through the steepest ascent experiment as oxaloacetate 0.208 6 g/L, calcium gluconate 0.048 2 g/L, and vitamin B_2 0.041 0 mg/L. Under the optimal conditions, the yield of gibberellin ...