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 effect s 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 bi oreactor could reach 3.90 g l(-1), more than 3-times greater than previousl y reported for submerged and solid fermentations. pH, rice flour concentrat ion and C:N ratio were the factors that most influenced the production of g ibberellic acid; pH being the most important. The response surface of gibbe rellic acid production to changes in pH and C:N ratio or rice flour concent ration 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 p roduction of gibberellic acid was also significant and greatest production was at 30 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.