The present study focused on the improvement of Saccharomyces cerevisiae through random mutagenesis for enhanced production of beta-D-fructofuranosidase (FFase) using sucrose salt media. Sixty strains of S. cerevisiae were isolated from different fruits and soil samples and screened for FFase production. Enzyme productivity of different yeast isolates ranged from 0.03 to 1.10 U/ml. The isolate with the highest activity was subjected to ultraviolet (UV) radiation and mutagenesis using N-methyl N-nitro N-nitroso guanidine (MNNG). One mutant produced FFase at a level of 17.8 +/- 0.9 U/ml. The MNNG-treated isolate was exposed to ethyl methane sulphonate (EMS), and a mutant with an enzyme activity of 25.56 +/- 1.4 U/ml was obtained. Further exposure to UV radiation and chemicals yielded a mutant exhibiting an activity of 34.12 +/- 1.8 U/ml. After optimization of incubation time (48 h), sucrose concentration (5.0 g/L), initial pH (6.0) and inoculum size (2.0% v/v), enzyme production reached 45.65 +/- 4.6 U/ml with a noticeable greater than 40-fold increase compared to the wild-type culture. On the basis of kinetic variables, notably Q(P) (0.723 +/- 0.2 U/g/h), Y-p/s, (2.036 +/- 0.05 U/g) and q(p) (0.091 +/- 0.02 U/g yeast cells/h), the mutant S. cerevisiae UME-2 was found to be a hyperproducer of FFase (LSD 0.054, p <= 0.05). (C) 2007 Elsevier Ltd. All rights reserved.