GLU activity was assayed using the method of Ippolito et al. (2000) with some modifications. Enzyme extract was dialyzed for 12 h at 4 ◦C and then centrifuged at 12,000 × g for 20 min at 4 ◦C. The supernatant (1 mL) was incubated with 0.1 mL of laminarin (0.5%, w/v) for 40 min at 37 ◦C. Afterward, 1 mL of the mixture was diluted at a ratio of 1:1 with distilled water. The reaction was stopped by addition of 3,5-dinitrosalicylate (1.5 mL) and boiling for 5 min in a water bath. The solution was diluted to 25 mL with distilled water, and the amount of reducing sugars was measured spectrophotometrically at 540 nm. One unit (U) was defined as the enzyme activity catalyzing the formation of one nanomole glucose equivalent per second. Enzyme activity was expressed as U kg−1 protein