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In this study, spores of inulinase-producing thermophilic Aspergillus tamarii were subjected to UV mutagenesis, and colonies obtained were screened for inulinase production on inulin-glucose agar. The thermal stability of the inulinase was also investigated. A mutant strain U4 was found to produce 2.8 times inulinase titre (62.1 U/mL) as against the wild strain (22.2 U/mL). Inulinase production by this U4 strain was also found not to be significantly (P≤ 0.05) affected by the presence of glucose. The inulinase produced retained 64% of its activity after incubation at 65ºC for three hours. Solid-state fermentation for inulinase production by the strain U4 showed that wheat bran supported the highest inulinase titre 218.3 U/gds while banana peels supported the lowest inulinase production titre of 80.5 U/gds. Further optimization of cultural parameters revealed that incubation time of 5 days, 60% initial moisture content of the substrate, 2% inoculum density 2%, temperature 55ºC and pH 4.5 were optimal for inulinase production. Under optimized conditions, inulinase titre of 426.6 U/gds was observed. The pattern of inulin hydrolysis by the inulinase revealed the presence of monosaccharide as the main product of hydrolysis. Inulinase