2.5. Inulinase activity assay
Inulinase activity was assayed by measuring the amount of reducing sugar fructose released from inulin, using Nelson’s method (1944). The reaction mixture containing 0.5 ml of enzyme extract and 0.5 ml of 1% (w/v) inulin in 0.2 M sodium acetate buffer (pH 5). The mixture was incubated at 50 ◦ C for 15 min. The amount of reducing sugars released was measured using Somogyi’s copper reagent. Absorbance was read at 520 nm. One unit of inulinase (IU) was defined as the amount of enzyme which librated 1 mol of fructose per min under the assay conditions. Results of the determi-nation of inulinase activity were presented in units of activity/gram solid substrate (U/gds).