Optimization of gibberellic acid production by immobilized Gibberella fujikuroi mycelium in fluidized bioreactors

An orthogonal experimental design L-9 (3(4)) was used to investigate effects of temperature, pH, C:N ratio (glucose-C, NH4Cl-N) and concentrations of rice flour on production of gibberellic acid by Gibberella fujikuroi in 3.5 1 fluidized bioreactors. The gibberellic acid production in a fluidized bioreactor could reach 3.90 g l(-1), more than 3-times greater than previously reported for submerged and solid fermentations. pH, rice flour concentration and C:N ratio were the factors that most influenced the production of gibberellic acid; pH being the most important. The response surface of gibberellic acid production to changes in pH and C:N ratio or rice flour concentration indicated that greatest production was found with a C:N ratio of 36.8 and pH 5 while the optimum concentration for rice flour was 2 g l(-1) and production increased with increased pH. The effect of temperature on the production of gibberellic acid was also significant and greatest production was at 30 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.