Gibberellic acid (GA) production from milk permeate was studied by 28 mutants of Fusarium moniliforme, among which mutant gamma-14 was selected as the best producer. Experiments were carried out in shaker flasks and fermentative process was analyzed with free and immobilized cells. Immobilization of mutant gamma-14 cells onto loofa sponge discs was studied with respect to the optimization of the incubation temperature, initial pH, inoculum size (number of discs) and its reusability for GA production. Best yield of GA (2.40 gl(-1)) was recorded by immobilized cells under optimized cultural conditions (4 immobilized discs, 30 degrees C and pH 5). Data obtained during four reusable cycles showed high stability of GA production and reduction in the initiation time of acid production, resulting in higher levels of GA in shorter time duration. Immobilization of mutant gamma-14 cells onto loofa sponge discs, permitted repeated reuse under the specified fermentation conditions for GA production from milk permeate. (C) 2008 Elsevier Ltd. All rights reserved