MUTAGENESIS OF ASPERGILLUS ORYZAE IPT-301 TO IMPROVE THE PRODUCTION OF β- FRUCTOFURANOSIDASE

Aspergillus oryzae IPT-301, previously reported as a β-fructofuranosidase producing microorganism, was successfully mutated using UV irradiation at 253.7 nm followed by the screening of survivors resistant to certain stress conditions. Strains were first subjected to the β-fructofuranosidase activity assay using a portion from the colony grown in Petri dish as the enzyme source. Seven mutants with β-fructofuranosidase activity values relative to the parent culture between 140- 190 % were selected from survivors grown at temperature of 40ºC or 0.018 % (w/v) sodium dodecyl sulfate concentration. They were cultivated on a rotary shaker to characterize mycelium and extracellular fructosyltransferase activities. Three mutants named IPT-745, IPT-746 and IPT-748 showed the highest amount of mycelium activity whose values increased 1.5- 1.8 fold, compared with the parent strain. It was found that more than 55 % of total enzyme activity (mycelium- plus extracellular- activity) from these strains was detected in the mycelium fraction. Only one mutant, IPT-747, exceeded the amount of extracellular enzyme exhibited by the parent strain (1.5 times). This mutant also showed the highest value of total fructosyltransferase activity. Key words: Aspergillus oryzae. Mutagenesis. β-fructofuranosidase. Fructosyltransferase