Selection of Aspergillus Niger Mutant Using Antimetabolite 2-deoxy D-glucose after N-methyl N-nitro N-nitroso Guanidine (mnng) Treatment

A xylan-degrading enzyme (endo ß-1,4 xylanase, EC 3.2.1.8) cleaves ß-1,4 glycosidic bond to produce xylose and is useful mainly in biobleaching paper pulp, pharmaceutical and food industries. The present investigation deals with the selection of derepressed mutant of Aspergillus niger GCBT-35 using antimetabolite 2-deoxy D-glucose (2DG) after N-methyl N-nitro N-nitroso guanidine (MNNG) treatment and optimization of cultural conditions for the enhanced xylanase production. Medium containing (g/l) wheat bran 20.0, NaNO3 1.0, NH4Cl 1.0, KH2PO4 1.0, CaCl2 1.0, MgSO4. 7H2O 0.3, meat extract 5.0 and Tween 80 1.5 ml was found to be best for xylanase production. The optimal production of xylanase (289.86 U/ml/min) was achieved 72 h after the conidial inoculation, when 1.0% (w/v) meat extract was used as a nitrogen source in the culture medium at an initial medium of 5.5 pH. This enhancement in xylanolytic activity is about 2.7 fold higher than that of wild culture.