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

Abstract

An orthogonal experimental design L 9 (3 4) was used to investigate effects of temperature, pH, C:N ratio (glucoseC, NH 4ClN) and concentrations of rice flour on production of gibberellic acid by Gibberella fujikuroi in 3.5 l 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°C.